%version; ]> Administrator Reference for Kea 2010-2014Internet Systems Consortium, Inc. Kea is an open source implementation of the Dynamic Host Configuration Protocol (DHCP) servers, developed and maintained by Internet Systems Consortium (ISC). This is the reference guide for Kea version &__VERSION__;. The most up-to-date version of this document (in PDF, HTML, and plain text formats), along with other documents for Kea, can be found at . This is the reference guide for Kea version &__VERSION__;. Kea is the next generation of DHCP servers developed by ISC. It supports both DHCPv4 and DHCPv6 protocols along with their extensions (e.g. prefix delegation). It also supports the dynamic updates to DNS. Kea has been initially developed as a part of the BIND 10 framework (). In early 2014, ISC made the decision to discontinue active development of BIND 10 and continue development of Kea as standalone DHCP servers. As a result, the components and libraries related to the BIND10 framework and DNS are going to be removed from the Kea source tree over time. In order to remove the dependency on Python 3, the BIND 10 framework will be replaced by the server startup and configuration mechanisms written in C++. Kea has been implemented in BIND 10 framework and to certain extent it still depends on various BIND 10 libraries. It also requires the BIND 10 framework to run, because BIND 10 configuration mechanisms are used to configure Kea. As a result, this document still refers to BIND 10 in many paragraphs. The term "BIND 10" in the context of this document means "BIND 10 libraries and applications which are necessary for Kea to run and configure". The term "Kea" means "the collection of binaries and libraries which, as a whole, implement the DHCP protocols. This guide covers Kea version &__VERSION__;.

Kea builds have been tested on (in no particular order) Debian GNU/Linux 6 and unstable, Ubuntu 9.10, NetBSD 5, Solaris 10 and 11, FreeBSD 7 and 8, CentOS Linux 5.3, MacOS 10.6 and 10.7, and OpenBSD 5.1. It has been tested on Sparc, i386, and amd64 hardware platforms. It is planned for Kea to build, install and run on Windows and standard Unix-type platforms.

Running Kea uses various extra software which may not be provided in some operating systems' default installations nor standard packages collections. You may need to install this required software separately. (For the build requirements, also see .) Kea was developed as a collection of applications within BIND 10 framework and it still relies on the remaining parts of this framework. In particular, the servers' configuration and startup are still facilitated by the modules which originate in BIND 10. These modules require at least Python 3.1 to run. They also work with Python 3.2 ()). The dependency on Python will be removed once a replacing configuration and startup mechanisms are developed for Kea. At this point Kea will be written in pure C++. Kea supports two crypto libraries: Botan and OpenSSL. Only one of them is required during compilation. Kea uses the Botan crypto library for C++ (). It requires at least Botan version 1.8. As an alternative to Botan, Kea can use the OpenSSL crypto library (). It requires a version with SHA-2 support. Kea uses the log4cplus C++ logging library (). It requires at least log4cplus version 1.0.3.

Kea is modular. Part of this modularity is accomplished using multiple cooperating processes which, together, provide the server functionality. At first, running many different processes may seem confusing. However, these processes are started by running a single command, bind10. This command starts a master process, b10-init, which will start other required processes and other processes when configured. The processes that may be started have names starting with "b10-", including: b10-cfgmgr — Configuration manager. This process maintains all of the configuration for BIND 10. b10-cmdctl — Command and control service. This process allows external control of the BIND 10 system. b10-dhcp4 — DHCPv4 server process. This process responds to DHCPv4 queries from clients. b10-dhcp6 — DHCPv6 server process. This process responds to DHCPv6 queries from clients. b10-dhcp-ddns — DHCP-DDNS process. This process acts as an intermediary between the DHCP servers and DNS server. It receives name update requests from the DHCP servers and sends DNS Update messages to the DNS servers. b10-msgq — Message bus daemon. This process coordinates communication between all of the other BIND 10 processes. b10-sockcreator — Socket creator daemon. This process creates sockets used by network-listening BIND 10 processes. b10-stats — Statistics collection daemon. This process collects and reports statistics data. b10-stats-httpd — HTTP server for statistics reporting. This process reports statistics data in XML format over HTTP. These do not need to be manually started independently.

Once BIND 10 is running, a few commands are used to interact directly with the system: bindctl — Interactive administration interface. This is a low-level command-line tool which allows a developer or an experienced administrator to control Kea. b10-cmdctl-usermgr — User access control. This tool allows an administrator to authorize additional users to manage Kea.

The tools and modules are covered in full detail in this guide. In addition, manual pages are also provided in the default installation. BIND 10 also provides libraries and programmer interfaces for C++ and Python for the message bus and configuration backend, and, of course, DHCP. These include detailed developer documentation and code examples. This quickly covers the standard steps for installing and deploying Kea. For further details, full customizations, and troubleshooting, see the respective chapters in the Kea guide.

Install required run-time and build dependencies. Checkout the latest Kea revision from the Git repository: $ git clone git://git.kea.isc.org/kea Go into the source and run configure: $ cd kea $ autoreconf --install $ ./configure Build it: $ make Install it as root (by default to prefix /usr/local/): $ make install Change directory to the install prefix (by default /usr/local/): $ cd /usr/local/ Create a user for yourself: $ sbin/b10-cmdctl-usermgr add root and enter a newly chosen password when prompted. Start the server (as root): $ sbin/bind10 DHCP components are not started in the default configuration. In another console, enable the DHCPv6 service (by using the bindctl utility to configure the b10-dhcp6 component to run): $ bin/bindctl (Login with the username and password you used above to create a user.) > config add Init/components b10-dhcp6 > config set Init/components/b10-dhcp6/kind dispensable > config commit > quit Test it; for example, use the ISC DHCP client to send DHCPv6 queries to the server and verify that the client receives a configuration from the server: $ dhclient -6

Some operating systems or software package vendors may provide ready-to-use, pre-built software packages for Kea. Installing a pre-built package means you do not need to install build-only prerequisites and do not need to make the software. FreeBSD ports, NetBSD pkgsrc, and Debian testing package collections provide all the prerequisite packages.

The following is the standard, common layout of the complete Kea installation: bin/ — general tools and diagnostic clients. etc/bind10/ — configuration files. lib/ — libraries and python modules. libexec/bind10/ — executables that a user wouldn't normally run directly and are not run independently. These are the BIND 10 and Kea modules which are daemons started by the b10-init master process. sbin/ — commands used by the system administrator. share/bind10/ — configuration specifications. share/doc/bind10/ — this guide and other supplementary documentation. share/man/ — manual pages (online documentation). var/bind10/ — data source and configuration databases.

In addition to the run-time requirements (listed in ), building Kea from source code requires various development include headers and program development tools. Some operating systems have split their distribution packages into a run-time and a development package. You will need to install the development package versions, which include header files and libraries, to build Kea from source code. Building from source code requires the Boost build-time headers (). At least Boost version 1.35 is required. To build Kea, also install the Botan (at least version 1.8) or OpenSSL, and the log4cplus (at least version 1.0.3) development include headers. Building Kea also requires a C++ compiler and standard development headers, make, and pkg-config. Kea builds have been tested with GCC g++ 3.4.3, 4.1.2, 4.1.3, 4.2.1, 4.3.2, and 4.4.1; Clang++ 2.8; and Sun C++ 5.10. Visit the user-contributed wiki at for system-specific installation tips.

Kea is open source software written in C++ (some components of the BIND 10 framework are written in Python). It is freely available in source code form from ISC as a downloadable tar file or via Kea Git code revision control service. (It may also be available in pre-compiled ready-to-use packages from operating system vendors.)

Kea 0.8 is available as a part of BIND10 1.2 release, which is a final release of BIND10 from ISC. This release can be downloaded from: .

Downloading this "bleeding edge" code is recommended only for developers or advanced users. Using development code in a production environment is not recommended. When using source code retrieved via Git, additional software will be required: automake (v1.11 or newer), libtoolize, and autoconf (2.59 or newer). These may need to be installed. The latest development code (and temporary experiments and un-reviewed code) is available via the Kea code revision control system. This is powered by Git and all the Kea development is public. The leading development is done in the master branch. The code can be checked out from git://git.kea.isc.org/kea; for example: $ git clone git://git.kea.isc.org/kea When checking out the code from the code version control system, it doesn't include the generated configure script, Makefile.in files, nor their related build files. They can be created by running autoreconf with the --install switch. This will run autoconf, aclocal, libtoolize, autoheader, automake, and related commands.

Kea uses the GNU Build System to discover build environment details. To generate the makefiles using the defaults, simply run: $ ./configure Run ./configure with the --help switch to view the different options. Some commonly-used options are: --prefix Define the installation location (the default is /usr/local/). --with-boost-include Define the path to find the Boost headers. --with-pythonpath Define the path to Python 3.1 if it is not in the standard execution path. --with-gtest Enable building the C++ Unit Tests using the Google Tests framework. Optionally this can define the path to the gtest header files and library. --with-openssl Replace Botan by OpenSSL for the crypto library. The default is to try to find a working Botan then OpenSSL only if not found. --without-werror Disable the default use of the -Werror compiler flag so that compiler warnings aren't build failures. For additional instructions concerning the building and installation of Kea for various databases, see . For additional instructions concerning configuration backends, see . For example, the following configures it to find the Boost headers, find the Python interpreter, and sets the installation location: $ ./configure \ --with-boost-include=/usr/pkg/include \ --with-pythonpath=/usr/pkg/bin/python3.1 \ --prefix=/opt/bind10 If the configure fails, it may be due to missing or old dependencies.

After the configure step is complete, to build the executables from the C++ code and prepare the Python scripts, run: $ make

To install the Kea executables, support files, and documentation, run: $ make install Please don't use any form of parallel or job server options (such as GNU make's -j option) when performing this step. Doing so may cause errors. The install step may require superuser privileges. If required, run ldconfig as root with /usr/local/lib (or with ${prefix}/lib if configured with --prefix) in /etc/ld.so.conf (or the relevant linker cache configuration file for your OS): $ ldconfig If you do not run ldconfig where it is required, you may see errors like the following: program: error while loading shared libraries: libkea-something.so.1: cannot open shared object file: No such file or directory

Kea is started with the bind10 command. It runs the b10-init daemon which starts up the required processes, and will also restart some processes that exit unexpectedly. bind10 is the only command needed to start Kea. After starting the b10-msgq communications channel, b10-init connects to it, runs the configuration manager, and reads its own configuration. Then it starts the other modules. The b10-sockcreator, b10-msgq and b10-cfgmgr services make up the core. The b10-msgq daemon provides the communication channel between every part of the system. The b10-cfgmgr daemon is always needed by every module, if only to send information about themselves somewhere, but more importantly to ask about their own settings, and about other modules. The b10-sockcreator daemon can allocate Internet addresses and ports needed by network services but is currently unused by DHCP servers. In its default configuration, the b10-init master process will also start up b10-cmdctl for administration tools to communicate with the system, and b10-stats for statistics collection. The DHCP servers are not started by default. The configuration of components to start is covered in .

To start the BIND 10 service, simply run bind10 as root. It will run in the foreground and your shell prompt will not be available. It will output various log messages as it starts up and is used. Run it with the --verbose switch to get additional debugging or diagnostic output. If the setproctitle Python module is detected at start up, the process names for the Python-based daemons will be renamed to better identify them instead of just python. This is not needed on some operating systems.

The BIND 10 components use the b10-msgq message routing daemon to communicate with Kea components. The b10-msgq implements what is called the Command Channel. Processes intercommunicate by sending messages on the command channel. Example messages include shutdown, get configurations, and set configurations. This Command Channel is not used for DNS message passing. It is used only to control and monitor the BIND 10 system. Administrators do not communicate directly with the b10-msgq daemon. By default, BIND 10 uses a UNIX domain socket file named /usr/local/var/bind10/msg_socket for this interprocess communication. The configuration manager, b10-cfgmgr, handles all system configuration. It provides persistent storage for configuration, and notifies running modules of configuration changes. The b10-dhcp6, b10-dhcp4 and b10-dhcp-ddns daemons receive their configurations from the configuration manager over the b10-msgq command channel. The administrator doesn't connect to it directly, but uses a user interface to communicate with the configuration manager via b10-cmdctl's REST-ful interface. b10-cmdctl is covered in . In future releases of Kea, the architecture which originates in the BIND 10 project will be replaced by the new mechanisms to start and configure Kea. The new mechanisms will use a file based configuration. The b10-cfgmgr daemon can send all specifications and all current settings to the bindctl client (via b10-cmdctl). b10-cfgmgr relays configurations received from b10-cmdctl to the appropriate modules. The stored configuration file is at /usr/local/var/bind10/b10-config.db. (The directory is what was defined at build configure time for --localstatedir. The default is /usr/local/var/.) The format is loosely based on JSON and is directly parseable python, but this may change in a future version. This configuration data file is not manually edited by the administrator. The configuration manager does not have any command line arguments. Normally it is not started manually, but is automatically started using the b10-init master process (as covered in ). b10-cmdctl is the gateway between administrators and the BIND 10 system. It is a HTTPS server that uses standard HTTP Digest Authentication for username and password validation. It provides a REST-ful interface for accessing and controlling BIND 10. When b10-cmdctl starts, it firsts asks b10-cfgmgr about what modules are running and what their configuration is (over the b10-msgq channel). Then it will start listening on HTTPS for clients — the user interface — such as bindctl. b10-cmdctl directly sends commands (received from the user interface) to the specified component. Configuration changes are actually commands to b10-cfgmgr so are sent there. The HTTPS server requires a private key, such as a RSA PRIVATE KEY. The default location is at /usr/local/etc/bind10/cmdctl-keyfile.pem. (A sample key is at /usr/local/share/bind10/cmdctl-keyfile.pem.) It also uses a certificate located at /usr/local/etc/bind10/cmdctl-certfile.pem. (A sample certificate is at /usr/local/share/bind10/cmdctl-certfile.pem.) This may be a self-signed certificate or purchased from a certification authority. The HTTPS server doesn't support a certificate request from a client (at this time). The b10-cmdctl daemon does not provide a public service. If any client wants to control BIND 10, then a certificate needs to be first received from the BIND 10 administrator. The Kea installation provides a sample PEM bundle that matches the sample key and certificate. The b10-cmdctl daemon also requires the user account file located at /usr/local/etc/bind10/cmdctl-accounts.csv. This comma-delimited file lists the accounts with a user name, hashed password, and salt. The administrator may create a user account with the b10-cmdctl-usermgr tool. By default the HTTPS server listens on the localhost port 8080. The port can be set by using the --port command line option. The address to listen on can be set using the --address command line argument. Each HTTPS connection is stateless and times out in 1200 seconds by default. This can be redefined by using the --idle-timeout command line argument.

The configuration items for b10-cmdctl are: accounts_file which defines the path to the user accounts database (the default is /usr/local/etc/bind10/cmdctl-accounts.csv); cert_file which defines the path to the PEM certificate file (the default is /usr/local/etc/bind10/cmdctl-certfile.pem); and key_file which defines the path to the PEM private key file (the default is /usr/local/etc/bind10/cmdctl-keyfile.pem).

bindctl has an internal command history, as well as tab-completion for most of the commands and arguments. However, these are only enabled if the python readline module is available on the system. If not, neither of these features will be supported. The bindctl tool provides an interactive prompt for configuring, controlling, and querying the Kea components. It communicates directly with a REST-ful interface over HTTPS provided by b10-cmdctl. It doesn't communicate to any other components directly.

-a <address>, --address=<address> IP address that BIND 10's b10-cmdctl module is listening on. By default, this is 127.0.0.1. -c <certificate file>, --certificate-chain=<certificate file> PEM-formatted server certificate file. When this option is given, bindctl will verify the server certificate using the given file as the root of the certificate chain. If not specified, bindctl does not validate the certificate. --csv-file-dir=<csv file> bindctl stores the username and password for logging in in a file called default_user.csv; this option specifies the directory where this file is stored and read from. When not specified, ~/.bind10/ is used. Currently, this file contains an unencrypted password. -h, --help Shows a short overview of the command-line options of bindctl, and exits. --version Shows the version of bindctl, and exits. -p <port number>, --port=<port number> Port number that BIND 10's b10-cmdctl module is listening on. By default, this is port 8080.

The bindctl tool is an interactive command-line tool, with dynamic commands depending on the BIND 10 modules that are running. There are a number of fixed commands that have no module and that are always available. The general syntax of a command is <module> <command> [argument(s)] For example, the Init module has a 'shutdown' command to shut down BIND 10, with an optional argument 'help': > Init shutdown help Command shutdown (Shut down BIND 10 and Kea) help (Get help for command) This command has no parameters There are no mandatory arguments, only the optional 'help'.

help is both a command and an option that is available to all other commands. When run as a command directly, it shows the available modules. > help usage: <module name> <command name> [param1 = value1 [, param2 = value2]] Type Tab character to get the hint of module/command/parameters. Type "help(? h)" for help on bindctl. Type "<module_name> help" for help on the specific module. Type "<module_name> <command_name> help" for help on the specific command. Available module names: (list of modules) When 'help' is used as a command to a module, it shows the supported commands for the module; for example: > Init help Module Init Master process Available commands: help Get help for module. shutdown Shut down BIND10 and Kea ping Ping the Init process show_processes List the running BIND10 and Kea processes And when added to a module command, it shows the description and parameters of that specific command; for example: > DhcpDdns shutdown help Command shutdown (Shuts down b10-dhcp-ddns module server.) help (Get help for command) Parameters: type (string, optional) values: normal (default), now, or drain_first

Commands can have arguments, which can be either optional or mandatory. They can be specified by name (e.g. <command> <argument name>=<argument value>), or positionally, (e.g. <command> <argument value 1> <argument value 2>). <command> help shows the arguments a command supports and which of those are mandatory, and in which order the arguments are expected if positional arguments are used. For example, the shutdown command of the DhcpDdns module, as shown in the last example of the previous section, has one optional argument which is appended right after the command: > DhcpDdns shutdown now But since the class is optional (defaulting to normal), leaving it out works as well: > DhcpDdns shutdown The arguments can also be provided with their names: > DhcpDdns shutdown type="now"

Each module has its own set of commands (if any), which will only be available if the module is running.

Configuration commands are used to view and change the configuration of BIND 10 and its modules. Module configuration is only shown if that module is running, but similar to commands, there are a number of top-level configuration items that are always available (for instance tsig_keys and data_sources). Configuration changes (set, unset, add and remove) are done locally first, and have no immediate effect. The changes can be viewed with config diff, and either reverted (config revert), or committed (config commit). In the latter case, all local changes are submitted to the configuration manager, which verifies them, and if they are accepted, applied and saved in persistent storage. When identifying items in configuration commands, the format is Module/example/item Sub-elements of names, lists and sets (see ) are separated with the '/' character, and list indices are identified with [<index>]; for example: Module/example/list[2]/foo

The following configuration commands are available: show [all] [item name] Shows the current configuration of the given item. If 'all' is given, it will recurse through the entire set, and show every nested value. show_json [item name] Shows the full configuration of the given item in JSON format. add <item name> [value] Add an entry to configuration list or a named set (see ). When adding to a list, the command has one optional argument, a value to add to the list. The value must be in correct JSON and complete. When adding to a named set, it has one mandatory parameter (the name to add), and an optional parameter value, similar to when adding to a list. In either case, when no value is given, an entry will be constructed with default values. remove Remove an item from a configuration list or a named set. When removing an item for a list, either the index needs to be specified, or the complete value of the element to remove must be specified (in JSON format). set <item name> <value> Directly set the value of the given item to the given value. unset <item name> Remove any user-specified value for the given item. diff Show all current local changes that have not been committed yet. revert Revert all local changes without committing them. commit Send all local changes to the configuration manager, which will validate them, and apply them if validation succeeds. go Go to a specific configuration part, similar to the 'cd' command in a shell. There are a number of problems with the current implementation of go within bindctl, and we recommend not using it for general cases.

Configuration data can be of different types, which can be modified in ways that depend on the types. There are a few syntax restrictions on these types, but only basic ones. Modules may impose additional restrictions on the values of elements. integer A basic integer; can be set directly with config set, to any integer value. The value must not be quoted, or else, it will be parsed as a string. real A basic floating point number; can be set directly with config set, to any floating point value. The value must not be quoted, or else, it will be parsed as a string. boolean A basic boolean value; can be set directly with config set, to either true or false. The value must not be quoted, or else, it will be parsed as a string. Integer values are not allowed. string A basic string value; can be set directly with config set to any string. Double quotation marks are optional. null This is a special type representing 'no value at all'; usable in compound structures that have optional elements that are not set. maps Maps are (pre-defined) compound collections of other elements of any other type. They are not usually modified directly, but their elements are. Every top-level element for a module is a map containing the configuration values for that map, which can themselves be maps again. Some map entries are optional. If they are, and currently have a value, the value can be unset by using either config unset <item name> or config set <item name> null. Maps can be modified as a whole, but using the full JSON representation of the entire map to set. Since this involves a lot of text, this is usually not recommended. Another example is the Logging virtual module, which is, like any module, a map, but it only contains one element: a list of loggers. Normally, an administrator would only modify that list (or its elements) directly, but it is possible to set the entire map in one command; for example: config set Logging { "loggers": [] } list A list is a compound list of other elements of the same type. Elements can be added with config add <list name> [value], and removed with config remove <list name> [value] or config remove <list name><index>. The index is of the form square bracket, number, square bracket (e.g. [0]), and it immediately follows the list name (there is no separator or space between them). List indices start with 0 for the first element. For addition, if the value is omitted, an entry with default values will be added. For removal, either the index or the full value (in JSON format) needs to be specified. Lists can also be used with config set, but like maps, only by specifying the entire list value in JSON format. For example, this command shows the renew-timer used for the second element of the list subnet4 in the Dhcp4 module: config show Dhcp4/subnet4[1]/renew-timer named set Named sets are similar to lists, in that they are sets of elements of the same type, but they are not indexed by numbers, but by strings. Values can be added with config add <item name> <string> [value] where 'string' is the name of the element. If 'value' is ommitted, default values will be used. Elements can be removed with config remove <item name> <string> Elements in a named set can be addressed similarly to maps. For example, the Init/components elements is a named set; adding, showing, and then removing an element can be done with the following three commands (note the '/'-character versus the space before 'example_module'): config add Init/components example_module config show Init/components/example_module config remove Init/components example_module any The 'any' type is a special type that can have any form. Apart from that, it must consist of elements as described in this chapter, there is no restriction on which element types are used. This type is used in places where different data formats could be used. Element modification commands depend on the actual type of the value. For instance, if the value of an 'any' element is a list, config add and config remove work as for other lists.

The execute command executes a set of commands, either from a file or from a pre-defined set. Currently, there are no pre-defined sets available. > execute file /tmp/example_commands The optional show argument may be used when executing a script from a file; for example: > execute file /tmp/example_commands show

Within sets of commands to be run with the execute command, a number of directives are supported: !echo <string> Prints the given string to bindctl's output. !verbose on Enables verbose mode; all following commands that are to be executed are also printed. !verbose off Disables verbose mode; following commands that are to be executed are no longer printed.

Within scripts, you can add or remove modules with the normal configuration commands for Init/components. However, as module configuration and commands do not show up until the module is running, it is currently not possible to add a module and set its configuration in one script. This will be addressed in the future, but for now the only option is to add and configure modules in separate commands and execute scripts.

This chapter explains how to control and configure the b10-init parent. The startup of this resident process that runs the BIND 10 daemons is covered in .

The BIND 10 suite may be shut down by stopping the parent b10-init process. This may be done by running the Init shutdown command at the bindctl prompt.

The processes to be used can be configured for b10-init to start, with the exception of the required b10-sockcreator, b10-msgq and b10-cfgmgr components. The configuration is in the Init/components section. Each element represents one component, which is an abstraction of a process. To add a process to the set, let's say the DHCPv6 server (which is not started by default), you would do this: > config add Init/components b10-dhcp6 > config set Init/components/b10-dhcp6/kind needed > config set Init/components/b10-dhcp6/priority 10 > config commit Now, what it means. We add an entry called b10-dhcp6. It is both a name used to reference this component in the configuration and the name of the process to start. Then we set some parameters on how to start it. The special (not used in the example above), was introduced to be used for the components which require some kind of special care during startup. One such component is the b10-cmdctl, which is always started by default. No other components use this setting and it should be left unset for them. The kind specifies how a failure of the component should be handled. If it is set to dispensable (the default unless you set something else), it will get started again if it fails. If it is set to needed and it fails at startup, the whole b10-init shuts down and exits with an error exit code. But if it fails some time later, it is just started again. If you set it to core, you indicate that the system is not usable without the component and if such component fails, the system shuts down no matter when the failure happened. This is the behavior of the core components (the ones you can't turn off), but you can declare any other components as core as well if you wish (but you can turn these off, they just can't fail). The priority defines order in which the components should start. The ones with higher numbers are started sooner than the ones with lower ones. If you don't set it, 0 (zero) is used as the priority. Usually, leaving it at the default is enough. There are other parameters we didn't use in our example. One of them is address. It is the address used by the component on the b10-msgq message bus. The special components already know their address, but the usual ones don't. The address is by convention the thing after b10-, with the first letter capitalized (eg. b10-stats would have Stats as its address). The last one is process. It is the name of the process to be started. It defaults to the name of the component if not set, but you can use this to override it. (The special components also already know their executable name.) The configuration is quite powerful, but that includes a lot of space for mistakes. You could turn off the b10-cmdctl, but then you couldn't change it back the usual way, as it would require it to be running (you would have to find and edit the configuration directly). In short, you should think twice before disabling something here. The running processes started by b10-init may be listed by running Init show_processes using bindctl.

The Dynamic Host Configuration Protocol for IPv4 (DHCP or DHCPv4) and Dynamic Host Configuration Protocol for IPv6 (DHCPv6) are protocols that allow one node (server) to provision configuration parameters to many hosts and devices (clients). To ease deployment in larger networks, additional nodes (relays) may be deployed that facilitate communication between servers and clients. Even though principles of both DHCPv4 and DHCPv6 are somewhat similar, these are two radically different protocols. Kea offers two server implementations, one for DHCPv4 and one for DHCPv6. The DHCPv4 component is colloquially referred to as Kea4 and its DHCPv6 counterpart is called Kea6. In addition to providing lease management services, both Kea4 and Kea6 can provide dynamic DNS (DDNS) updates driven by the lease changes they make. These updates are carried out with the assistance of the DHCP-DDNS server, colloquially referred to as D2. When configured to do so, Kea servers will notify D2 of lease changes. D2 will match them to the appropriate DNS servers and instruct those severs to add or delete the requisite DNS entries. This chapter covers those parts of Kea that are common to both servers. DHCPv4-specific details are covered in , while those details specific to DHCPv6 are described in . The DHCP-DDNS server details are covered in

Kea 0.9 introduces configuration backends that are switchable during compilation phase. There is a new parameter for configure script: --with-kea-config. It currently supports two values: BIND10 and JSON. This is currently only supported by DHCPv6 component. BIND10 BIND10 (which is the default value as of April 2014) means that Kea6 is linked with the BIND10 configuration backend that connects to the BIND10 framework and in general works exactly the same as Kea 0.8 and earlier versions. The benefits of that backend are uniform integration with BIND10 framework, easy on-line reconfiguration using bindctl, available RESTful API. On the other hand, it requires the whole heavy BIND10 framework that requires Python3 to be present. That backend is likely to go away with the release of Kea 0.9. JSON JSON is a new configuration backend that causes Kea to read JSON configuration file from disk. It does not require any framework and thus is considered more lightweight. It will allow dynamic on-line reconfiguration, but will lack remote capabilities (i.e. no RESTful API). This configuration backend is expected to be the default for upcoming Kea 0.9.

Kea stores its leases in a lease database. The software has been written in a way that makes it possible to choose which database product should be used to store the lease information. At present, Kea supports 3 database backends: MySQL, PostgreSQL and Memfile. To limit external dependencies, both MySQL and PostgreSQL support are disabled by default and only Memfile (which is implemented in pure C++) is available. Support for a given database backend must be explicitly included when Kea is built. This section covers the building of Kea with MySQL and/or PostgreSQL and the creation of the lease database.

Install MySQL according to the instructions for your system. The client development libraries must be installed. Build and install Kea as described in , with the following modification: to enable the MySQL database code, at the "configure" step (see ), specify the location of the MySQL configuration program "mysql_config" with the "--with-dhcp-mysql" switch, i.e. ./configure [other-options] --with-dhcp-mysql ...if MySQL was installed in the default location, or: ./configure [other-options] --with-dhcp-mysql=path-to-mysql_config ...if not.

The next task is to create both the lease database and the user under which the servers will access it. A number of steps are required: 1. Log into MySQL as "root": $ mysql -u root -p Enter password: : mysql> 2. Create the database: mysql> CREATE DATABASE database-name; ... database-name is the name you have chosen for the database. 3. Create the database tables: mysql> CONNECT database-name; mysql> SOURCE path-to-bind10/share/bind10/dhcpdb_create.mysql 4. Create the user under which BIND 10 will access the database (and give it a password), then grant it access to the database tables: mysql> CREATE USER 'user-name'@'localhost' IDENTIFIED BY 'password'; mysql> GRANT ALL ON database-name.* TO 'user-name'@'localhost'; 5. Exit MySQL: mysql> quit Bye $

Install PostgreSQL according to the instructions for your system. The client development libraries must be installed. Client development libraries are often packaged as "libpq". Build and install Kea as described in , with the following modification: to enable the PostgreSQL database code, at the "configure" step (see ), specify the location of the PostgreSQL configuration program "pg_config" with the "--with-dhcp-pgsql" switch, i.e. ./configure [other-options] --with-dhcp-pgsql ...if PostgreSQL was installed in the default location, or: ./configure [other-options] --with-dhcp-pgsql=path-to-pg_config ...if not.

The next task is to create both the lease database and the user under which the servers will access it. A number of steps are required: 1. Log into PostgreSQL as "root": $ sudo -u postgres psql postgres Enter password: : postgres=# 2. Create the database: postgres=# CREATE DATABASE database-name; CREATE DATABASE postgres=# ... database-name is the name you have chosen for the database. 3. Create the user under which Kea will access the database (and give it a password), then grant it access to the database: postgres=# CREATE USER user-name WITH PASSWORD 'password'; CREATE ROLE postgres=# postgres=# GRANT ALL PRIVILEGES ON DATABASE database-name TO user-name; GRANT postgres=# 4. Exit PostgreSQL: postgres=# \q Bye $ 5. Create the database tables using the new user's credentials. After entering the following command, you will be prompted for the new user's password. When the command completes you will be returned to the shell prompt. You should see output similar to following: $ psql -d database-name -U user-name -f path-to-bind10/share/bind10/dhcpdb_create.pgsql Password for user user-name: CREATE TABLE CREATE INDEX CREATE INDEX CREATE TABLE CREATE INDEX CREATE TABLE START TRANSACTION INSERT 0 1 INSERT 0 1 INSERT 0 1 COMMIT CREATE TABLE START TRANSACTION INSERT 0 1 COMMIT $ If instead you encounter an error such as shown below: psql: FATAL: no pg_hba.conf entry for host "[local]", user "user-name", database "database-name", SSL off This indicates that the PostgreSQL configuration needs to be modified. Kea uses password authentication when connecting to the database and must have the appropriate entries added to PostgreSQL's pg_hba.conf file. This file is normally located in the primary data directory for your PostgreSQL server. The precise path may vary but the default location for PostgreSQL 9.3 on Centos 6.5 is: /var/lib/pgsql/9.3/data/pg_hba.conf. Assuming Kea is running on the same host as PostgreSQL, adding lines similar to following should be sufficient to provide password-authenticated access to Kea's database: local database-name user-name password host database-name user-name 127.0.0.1/32 password host database-name user-name ::1/128 password Please consult your PostgreSQL user manual before making these changes as they may expose your other databases that you run on the same system.

b10-dhcp4 is the Kea DHCPv4 server and is configured through the bindctl program. After starting bind10 and entering bindctl, the first step in configuring the server is to add it to the list of running services. > config add Init/components b10-dhcp4 > config set Init/components/b10-dhcp4/kind dispensable > config commit To remove b10-dhcp4 from the set of running services, the b10-dhcp4 is removed from list of Init components: > config remove Init/components b10-dhcp4 > config commit Note that the server was only removed from the list, so BIND10 will not restart it, but the server itself is still running. Hence it is usually desired to stop it: > Dhcp4 shutdown On start-up, the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces that are up, running, are not loopback, and have IPv4 address assigned. The server will then listen to incoming traffic. Currently supported client messages are DISCOVER and REQUEST. The server will respond to them with OFFER and ACK, respectively. Since the DHCPv4 server opens privileged ports, it requires root access. Make sure you run this daemon as root.

Once the server is started, it can be configured. To view the current configuration, use the following command in bindctl: > config show Dhcp4 When starting the DHCPv4 daemon for the first time, the default configuration will be available. It will look similar to this: > config show Dhcp4 Dhcp4/hooks-libraries [] list (default) Dhcp4/interfaces/ list Dhcp4/renew-timer 1800 integer Dhcp4/rebind-timer 2000 integer (default) Dhcp4/valid-lifetime 4000 integer (default) Dhcp4/next-server "" string (default) Dhcp4/echo-client-id true boolean (default) Dhcp4/option-def [] list (default) Dhcp4/option-data [] list (default) Dhcp4/lease-database/type "" string (default) Dhcp4/lease-database/name "" string (default) Dhcp4/lease-database/user "" string (default) Dhcp4/lease-database/host "" string (default) Dhcp4/lease-database/password "" string (default) Dhcp4/subnet4/ list Dhcp4/dhcp-ddns/enable-updates true boolean Dhcp4/dhcp-ddns/server-ip "127.0.0.1" string Dhcp4/dhcp-ddns/server-port 53001 integer Dhcp4/dhcp-ddns/sender-ip "" string Dhcp4/dhcp-ddns/sender-port 0 integer Dhcp4/dhcp-ddns/max-queue-size 1024 integer Dhcp4/dhcp-ddns/ncr-protocol "UDP" string Dhcp4/dhcp-ddns/ncr-format "JSON" string Dhcp4/dhcp-ddns/override-no-update false boolean Dhcp4/dhcp-ddns/override-client-update false boolean Dhcp4/dhcp-ddns/replace-client-name false boolean Dhcp4/dhcp-ddns/generated-prefix "myhost" string Dhcp4/dhcp-ddns/qualifying-suffix "example.com" string To change one of the parameters, simply follow the usual bindctl procedure. For example, to make the leases longer, change their valid-lifetime parameter: > config set Dhcp4/valid-lifetime 7200 > config commit Please note that most Dhcp4 parameters are of global scope and apply to all defined subnets, unless they are overridden on a per-subnet basis. The renew-timer and rebind-timer are optional. If they are not specified, the DHCPv4 options 58 and 59 are not sent in the server's response to the client.

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database. describes one way to do it. By default, the server will use a CSV file rather than a database to store lease information. One of the advantages of using a file is that it eliminates dependency on third party database software. The configuration of the file backend (Memfile) is controlled through the Dhcp4/lease-database parameters. When default parameters are used, the Memfile backend will write leases to a disk in the [bind10-install-dir]/var/bind10/kea-leases4.csv. It is possible to alter the default location of the lease file. The following configuration: > config set Dhcp4/lease-database/type "memfile" > config set Dhcp4/lease-database/persist true > config set Dhcp4/lease-database/name "/tmp/kea-leases4.csv" > config commit will change the default location of the lease file to /tmp/kea-leases4.csv. The "persist" parameter controls whether the leases are written to disk. It is strongly recommended that this parameter is set to "true" at all times during the normal operation of the server

All leases issued by the server are stored in the lease database. Currently there are 3 database backends available: MySQL, PostgreSQL and memfile. The server comes with an in-memory database ("memfile") configured as the default database. This is used for internal testing and is not supported. In addition, it does not store lease information on disk: lease information will be lost if the server is restarted. , and so the server must be configured to access the correct database with the appropriate credentials. Database access information must be configured for the DHCPv4 server, even if it has already been configured for the DHCPv6 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database. Database configuration is controlled through the Dhcp4/lease-database parameters. The type of the database must be set to "mysql", "postgresql" or "memfile": > config set Dhcp4/lease-database/type "mysql" Next, the name of the database is to hold the leases must be set: this is the name used when the lease database was created (see or ). > config set Dhcp4/lease-database/name "database-name" If the database is located on a different system to the DHCPv4 server, the database host name must also be specified (although note that this configuration may have a severe impact on server performance): > config set Dhcp4/lease-database/host "remote-host-name" The usual state of affairs will be to have the database on the same machine as the DHCPv4 server. In this case, set the value to the empty string (this is the default): > config set Dhcp4/lease-database/host "" Finally, the credentials of the account under which the server will access the database should be set: > config set Dhcp4/lease-database/user "user-name" > config set Dhcp4/lease-database/password "password" If there is no password to the account, set the password to the empty string "". (This is also the default.) The password is echoed when entered and is stored in clear text in the configuration database. Improved password security will be added in a future version of Kea.

When DHCPv4 server starts up, by default it will listen to the DHCP traffic and respond to it on all interfaces detected during startup. However, in many cases it is desired to configure the server to listen and respond on selected interfaces only. The sample commands in this section show how to make interface selection using bindctl. The default configuration can be presented with the following command: > config show Dhcp4/interfaces Dhcp4/interfaces[0] "*" string An asterisk sign plays a role of the wildcard and means "listen on all interfaces". In order to override the default configuration, the existing entry can be replaced with the actual interface name: > config set Dhcp4/interfaces[0] eth1 > config commit Other interface names can be added on one-by-one basis: > config add Dhcp4/interfaces eth2 > config commit Configuration will now contain two interfaces which can be presented as follows: > config show Dhcp4/interfaces Dhcp4/interfaces[0] "eth1" string Dhcp4/interfaces[1] "eth2" string When configuration gets committed, the server will start to listen on eth1 and eth2 interfaces only. It is possible to use wildcard interface name (asterisk) concurrently with explicit interface names: > config add Dhcp4/interfaces * > config commit This will result in the following configuration: > config show Dhcp4/interfaces Dhcp4/interfaces[0] "eth1" string Dhcp4/interfaces[1] "eth2" string Dhcp4/interfaces[2] "*" string The presence of the wildcard name implies that server will listen on all interfaces. In order to fall back to the previous configuration when server listens on eth1 and eth2: > config remove Dhcp4/interfaces[2] > config commit

Subnet identifier is a unique number associated with a particular subnet. In principle, it is used to associate clients' leases with respective subnets. When subnet identifier is not specified for a subnet being configured, it will be automatically assigned by the configuration mechanism. The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet: 1, 2, 3 .... If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are 4 subnets and 3rd is removed the last subnet will be assigned identifier that the 3rd subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with the subnet 4, which may have unexpected consequences. In the future it is planned to implement the mechanism to preserve auto-generated subnet ids upon removal of one of the subnets. Currently, the only remedy for this issue is to manually specify the unique subnet identifier for each subnet. The following configuration: > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24" > config set Dhcp4/subnet4[0]/id 1024 > config commit will assign the arbitrary subnet identifier to the newly configured subnet. This identifier will not change for this subnet until "id" parameter is removed or set to 0. The value of 0 forces auto-generation of subnet identifier.

The essential role of DHCPv4 server is address assignment. The server has to be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The Administrator of that network has decided that addresses from range 192.0.2.10 to 192.0.2.20 are going to be managed by the Dhcp4 server. Such a configuration can be achieved in the following way: > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24" > config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ] > config commit Note that subnet is defined as a simple string, but the pool parameter is actually a list of pools: for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified. It is possible to define more than one pool in a subnet: continuing the previous example, further assume that 192.0.2.64/26 should be also be managed by the server. It could be written as 192.0.2.64 to 192.0.2.127. Alternatively, it can be expressed more simply as 192.0.2.64/26. Both formats are supported by Dhcp4 and can be mixed in the pool list. For example, one could define the following pools: > config set Dhcp4/subnet4[0]/pool [ "192.0.2.10-192.0.2.20", "192.0.2.64/26" ] > config commit The number of pools is not limited, but for performance reasons it is recommended to use as few as possible. Space and tabulations in pool definitions are ignored, so spaces before and after hyphen are optional. They can be used to improve readability. The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following: > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[1]/subnet "192.0.3.0/24" > config set Dhcp4/subnet4[1]/pool [ "192.0.3.0/24" ] > config commit Arrays are counted from 0. subnet[0] refers to the subnet defined in the previous example. The config add Dhcp4/subnet4 command adds another (second) subnet. It can be referred to as Dhcp4/subnet4[1]. In this example, we allow server to dynamically assign all addresses available in the whole subnet. When configuring a DHCPv4 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server should use a given pool, it will be able to allocate also first (typically network address) and the last (typically broadcast address) address from that pool. In the aforementioned example of pool 192.0.3.0/24, both 192.0.3.0 and 192.0.3.255 addresses may be assigned as well. This may be invalid in some network configurations. If you want to avoid this, please use the "min-max" notation.

One of the major features of DHCPv4 server is to provide configuration options to clients. Although there are several options that require special behavior, most options are sent by the server only if the client explicitly requested them. The following example shows how to configure DNS servers, which is one of the most frequently used options. Options specified in this way are considered global and apply to all configured subnets. > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "domain-name-servers" > config set Dhcp4/option-data[0]/code 6 > config set Dhcp4/option-data[0]/space "dhcp4" > config set Dhcp4/option-data[0]/csv-format true > config set Dhcp4/option-data[0]/data "192.0.3.1, 192.0.3.2" > config commit The first line creates new entry in option-data table. It contains information on all global options that the server is supposed to configure in all subnets. The second line specifies option name. For a complete list of currently supported names, see below. The third line specifies option code, which must match one of the values from that list. Line 4 specifies option space, which must always be set to "dhcp4" as these are standard DHCPv4 options. For other option spaces, including custom option spaces, see . The fifth line specifies the format in which the data will be entered: use of CSV (comma separated values) is recommended. The sixth line gives the actual value to be sent to clients. Data is specified as a normal text, with values separated by commas if more than one value is allowed. Options can also be configured as hexadecimal values. If csv-format is set to false, option data must be specified as a hex string. The following commands configure the domain-name-servers option for all subnets with the following addresses: 192.0.3.1 and 192.0.3.2. Note that csv-format is set to false. > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "domain-name-servers" > config set Dhcp4/option-data[0]/code 6 > config set Dhcp4/option-data[0]/space "dhcp4" > config set Dhcp4/option-data[0]/csv-format false > config set Dhcp4/option-data[0]/data "C0 00 03 01 C0 00 03 02" > config commit It is possible to override options on a per-subnet basis. If clients connected to most of your subnets are expected to get the same values of a given option, you should use global options: you can then override specific values for a small number of subnets. On the other hand, if you use different values in each subnet, it does not make sense to specify global option values (Dhcp4/option-data), rather you should set only subnet-specific values (Dhcp4/subnet[X]/option-data[Y]). The following commands override the global DNS servers option for a particular subnet, setting a single DNS server with address 192.0.2.3. > config add Dhcp4/subnet4[0]/option-data > config set Dhcp4/subnet4[0]/option-data[0]/name "domain-name-servers" > config set Dhcp4/subnet4[0]/option-data[0]/code 6 > config set Dhcp4/subnet4[0]/option-data[0]/space "dhcp4" > config set Dhcp4/subnet4[0]/option-data[0]/csv-format true > config set Dhcp4/subnet4[0]/option-data[0]/data "192.0.2.3" > config commit In a future version of Kea, it will not be necessary to specify the option code, space and csv-format fields as they will be set automatically. The currently supported standard DHCPv4 options are listed in and . The "Name" and "Code" are the values that should be used as a name in the option-data structures. "Type" designates the format of the data: the meanings of the various types is given in . Some options are designated as arrays, which means that more than one value is allowed in such an option. For example the option time-servers allows the specification of more than one IPv4 address, so allowing clients to obtain the the addresses of multiple NTP servers. The describes the configuration syntax to create custom option definitions (formats). It is generally not allowed to create custom definitions for standard options, even if the definition being created matches the actual option format defined in the RFCs. There is an exception from this rule for standard options for which Kea does not provide a definition yet. In order to use such options, a server administrator must create a definition as described in in the 'dhcp4' option space. This definition should match the option format described in the relevant RFC but configuration mechanism would allow any option format as it has no means to validate it at the moment. Name Code Type Array? subnet-mask1ipv4-addressfalsetime-offset2int32falserouters3ipv4-addresstruetime-servers4ipv4-addresstruename-servers5ipv4-addressfalsedomain-name-servers6ipv4-addresstruelog-servers7ipv4-addresstruecookie-servers8ipv4-addresstruelpr-servers9ipv4-addresstrueimpress-servers10ipv4-addresstrueresource-location-servers11ipv4-addresstruehost-name12stringfalseboot-size13uint16falsemerit-dump14stringfalsedomain-name15fqdnfalseswap-server16ipv4-addressfalseroot-path17stringfalseextensions-path18stringfalseip-forwarding19booleanfalsenon-local-source-routing20booleanfalsepolicy-filter21ipv4-addresstruemax-dgram-reassembly22uint16falsedefault-ip-ttl23uint8falsepath-mtu-aging-timeout24uint32falsepath-mtu-plateau-table25uint16trueinterface-mtu26uint16falseall-subnets-local27booleanfalsebroadcast-address28ipv4-addressfalseperform-mask-discovery29booleanfalsemask-supplier30booleanfalserouter-discovery31booleanfalserouter-solicitation-address32ipv4-addressfalsestatic-routes33ipv4-addresstruetrailer-encapsulation34booleanfalsearp-cache-timeout35uint32falseieee802-3-encapsulation36booleanfalsedefault-tcp-ttl37uint8falsetcp-keepalive-internal38uint32falsetcp-keepalive-garbage39booleanfalse Name Code Type Array? nis-domain40stringfalsenis-servers41ipv4-addresstruentp-servers42ipv4-addresstruevendor-encapsulated-options43emptyfalsenetbios-name-servers44ipv4-addresstruenetbios-dd-server45ipv4-addresstruenetbios-node-type46uint8falsenetbios-scope47stringfalsefont-servers48ipv4-addresstruex-display-manager49ipv4-addresstruedhcp-requested-address50ipv4-addressfalsedhcp-option-overload52uint8falsedhcp-message56stringfalsedhcp-max-message-size57uint16falsevendor-class-identifier60binaryfalsenwip-domain-name62stringfalsenwip-suboptions63binaryfalsetftp-server-name66stringfalseboot-file-name67stringfalseuser-class77binaryfalsefqdn81recordfalsedhcp-agent-options82emptyfalseauthenticate90binaryfalseclient-last-transaction-time91uint32falseassociated-ip92ipv4-addresstruesubnet-selection118ipv4-addressfalsedomain-search119binaryfalsevivco-suboptions124binaryfalsevivso-suboptions125binaryfalse NameMeaningbinaryAn arbitrary string of bytes, specified as a set of hexadecimal digits.booleanBoolean value with allowed values true or falseemptyNo value, data is carried in suboptionsfqdnFully qualified domain name (e.g. www.example.com)ipv4-addressIPv4 address in the usual dotted-decimal notation (e.g. 192.0.2.1)ipv6-addressIPv6 address in the usual colon notation (e.g. 2001:db8::1)recordStructured data that may comprise any types (except "record" and "empty")stringAny textuint88 bit unsigned integer with allowed values 0 to 255uint1616 bit unsinged integer with allowed values 0 to 65535uint3232 bit unsigned integer with allowed values 0 to 4294967295

It is also possible to define options other than the standard ones. Assume that we want to define a new DHCPv4 option called "foo" which will have code 222 and will convey a single unsigned 32 bit integer value. We can define such an option by using the following commands: > config add Dhcp4/option-def > config set Dhcp4/option-def[0]/name "foo" > config set Dhcp4/option-def[0]/code 222 > config set Dhcp4/option-def[0]/type "uint32" > config set Dhcp4/option-def[0]/array false > config set Dhcp4/option-def[0]/record-types "" > config set Dhcp4/option-def[0]/space "dhcp4" > config set Dhcp4/option-def[0]/encapsulate "" > config commit The "false" value of the "array" parameter determines that the option does NOT comprise an array of "uint32" values but rather a single value. Two other parameters have been left blank: "record-types" and "encapsulate". The former specifies the comma separated list of option data fields if the option comprises a record of data fields. The "record-fields" value should be non-empty if the "type" is set to "record". Otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space it should be left blank. Note that the above set of comments define the format of the new option and do not set its values. In the current release the default values are not propagated to the parser when the new configuration is being set. Therefore, all parameters must be specified at all times, even if their values are left blank. Once the new option format is defined, its value is set in the same way as for a standard option. For example the following commands set a global value that applies to all subnets. > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "foo" > config set Dhcp4/option-data[0]/code 222 > config set Dhcp4/option-data[0]/space "dhcp4" > config set Dhcp4/option-data[0]/csv-format true > config set Dhcp4/option-data[0]/data "12345" > config commit New options can take more complex forms than simple use of primitives (uint8, string, ipv4-address etc): it is possible to define an option comprising a number of existing primitives. Assume we want to define a new option that will consist of an IPv4 address, followed by unsigned 16 bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way: > config add Dhcp4/option-def > config set Dhcp4/option-def[0]/name "bar" > config set Dhcp4/option-def[0]/code 223 > config set Dhcp4/option-def[0]/space "dhcp4" > config set Dhcp4/option-def[0]/type "record" > config set Dhcp4/option-def[0]/array false > config set Dhcp4/option-def[0]/record-types "ipv4-address, uint16, boolean, string" > config set Dhcp4/option-def[0]/encapsulate "" The "type" is set to "record" to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the "record-types" field and should be those listed in . The values of the option are set as follows: > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "bar" > config set Dhcp4/option-data[0]/space "dhcp4" > config set Dhcp4/option-data[0]/code 223 > config set Dhcp4/option-data[0]/csv-format true > config set Dhcp4/option-data[0]/data "192.0.2.100, 123, true, Hello World" > config commit "csv-format" is set "true" to indicate that the "data" field comprises a command-separated list of values. The values in the "data" must correspond to the types set in the "record-types" field of the option definition. It is recommended that boolean values are specified using "true" and "false" strings. This helps to prevent errors when typing multiple comma separated values, as it make it easier to identify the type of the value being typed, and compare it with the order of data fields. Nevertheless, it is possible to use integer values: "1" and "0", instead of "true" and "false" accordingly. If other integer value is specified, the configuration is rejected.

Currently there are three option spaces defined: dhcp4 (to be used in DHCPv4 daemon) and dhcp6 (for the DHCPv6 daemon); there is also vendor-encapsulated-options-space, which is empty by default, but options can be defined in it. Those options are called vendor-specific information options. The following examples show how to define an option "foo" with code 1 that consists of an IPv4 address, an unsigned 16 bit integer and a string. The "foo" option is conveyed in a vendor specific information option. The first step is to define the format of the option: > config add Dhcp4/option-def > config set Dhcp4/option-def[0]/name "foo" > config set Dhcp4/option-def[0]/code 1 > config set Dhcp4/option-def[0]/space "vendor-encapsulated-options-space" > config set Dhcp4/option-def[0]/type "record" > config set Dhcp4/option-def[0]/array false > config set Dhcp4/option-def[0]/record-types "ipv4-address, uint16, string" > config set Dhcp4/option-def[0]/encapsulates "" > config commit (Note that the option space is set to "vendor-encapsulated-options-space".) Once the option format is defined, the next step is to define actual values for that option: > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "foo" > config set Dhcp4/option-data[0]/space "vendor-encapsulated-options-space" > config set Dhcp4/option-data[0]/code 1 > config set Dhcp4/option-data[0]/csv-format true > config set Dhcp4/option-data[0]/data "192.0.2.3, 123, Hello World" > config commit We also set up a dummy value for vendor-opts, the option that conveys our sub-option "foo". This is required else the option will not be included in messages sent to the client. > config add Dhcp4/option-data > config set Dhcp4/option-data[1]/name "vendor-encapsulated-options" > config set Dhcp4/option-data[1]/space "dhcp4" > config set Dhcp4/option-data[1]/code 43 > config set Dhcp4/option-data[1]/csv-format false > config set Dhcp4/option-data[1]/data "" > config commit With this version of Kea, the "vendor-encapsulated-options" option must be specified in the configuration although it has no configurable parameters. If it is not specified, the server will assume that it is not configured and will not send it to a client. In the future there will be no need to include this option in the configuration.

It is sometimes useful to define completely new option space. This is the case when user creates new option in the standard option space ("dhcp4 or "dhcp6") and wants this option to convey sub-options. Thanks to being in the separate space, sub-option codes will have a separate numbering scheme and may overlap with codes of standard options. Note that creation of a new option space when defining sub-options for a standard option is not required, because it is created by default if the standard option is meant to convey any sub-options (see ). Assume that we want to have a DHCPv4 option called "container" with code 222 that conveys two sub-options with codes 1 and 2. First we need to define the new sub-options: > config add Dhcp4/option-def > config set Dhcp4/option-def[0]/name "subopt1" > config set Dhcp4/option-def[0]/code 1 > config set Dhcp4/option-def[0]/space "isc" > config set Dhcp4/option-def[0]/type "ipv4-address" > config set Dhcp4/option-def[0]/record-types "" > config set Dhcp4/option-def[0]/array false > config set Dhcp4/option-def[0]/encapsulate "" > config commit > config add Dhcp4/option-def > config set Dhcp4/option-def[1]/name "subopt2" > config set Dhcp4/option-def[1]/code 2 > config set Dhcp4/option-def[1]/space "isc" > config set Dhcp4/option-def[1]/type "string" > config set Dhcp4/option-def[1]/record-types "" > config set Dhcp4/option-def[1]/array false > config set Dhcp4/option-def[1]/encapsulate "" > config commit Note that we have defined the options to belong to a new option space (in this case, "isc"). The next step is to define a regular DHCPv4 option with our desired code and specify that it should include options from the new option space: > add Dhcp4/option-def > set Dhcp4/option-def[2]/name "container" > set Dhcp4/option-def[2]/code 222 > set Dhcp4/option-def[2]/space "dhcp4" > set Dhcp4/option-def[2]/type "empty" > set Dhcp4/option-def[2]/array false > set Dhcp4/option-def[2]/record-types "" > set Dhcp4/option-def[2]/encapsulate "isc" > commit The name of the option space in which the sub-options are defined is set in the "encapsulate" field. The "type" field is set to "empty" to indicate that this option does not carry any data other than sub-options. Finally, we can set values for the new options: > config add Dhcp4/option-data > config set Dhcp4/option-data[0]/name "subopt1" > config set Dhcp4/option-data[0]/space "isc" > config set Dhcp4/option-data[0]/code 1 > config set Dhcp4/option-data[0]/csv-format true > config set Dhcp4/option-data[0]/data "192.0.2.3" > config commit > config add Dhcp4/option-data > config set Dhcp4/option-data[1]/name "subopt2" > config set Dhcp4/option-data[1]/space "isc" > config set Dhcp4/option-data[1]/code 2 > config set Dhcp4/option-data[1]/csv-format true > config set Dhcp4/option-data[1]/data "Hello world" > config commit > config add Dhcp4/option-data > config set Dhcp4/option-data[2]/name "container" > config set Dhcp4/option-data[2]/space "dhcp4" > config set Dhcp4/option-data[2]/code 222 > config set Dhcp4/option-data[2]/csv-format true > config set Dhcp4/option-data[2]/data "" > config commit Even though the "container" option does not carry any data except sub-options, the "data" field must be explicitly set to an empty value. This is required because in the current version of BIND 10 DHCP, the default configuration values are not propagated to the configuration parsers: if the "data" is not set the parser will assume that this parameter is not specified and an error will be reported. Note that it is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the "container" option from the previous example was required to carry an uint16 value as well as the sub-options, the "type" value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the "data" parameter - which should be a valid integer enclosed in quotes, e.g. "123" - would then be assigned to the uint16 field in the "container" option.

DHCPv4 server has been extended to support limited client classification. Although the current capability is modest, it is expected to be expanded in the future. It is envisaged that the majority of client classification extensions will be using hooks extensions. In certain cases it is useful to differentiate between different types of clients and treat them differently. The process of doing classification is conducted in two steps. The first step is to assess incoming packet and assign it to zero or more classes. This classification is currently simple, but is expected to grow in capability soon. Currently the server checks whether incoming packet has vendor class identifier option (60). If it has, content of that option is prepended with "VENDOR_CLASS_" then is interpreted as a class. For example, modern cable modems will send this option with value "docsis3.0" and as a result the packet will belong to class "VENDOR_CLASS_docsis3.0". It is envisaged that the client classification will be used for changing behavior of almost any part of the DHCP message processing, including assigning leases from different pools, assigning different option (or different values of the same options) etc. For now, there are only two mechanisms that are taking advantage of client classification: specific processing for cable modems and subnet selection. For clients that belong to the VENDOR_CLASS_docsis3.0 class, the siaddr field is set to the value of next-server (if specified in a subnet). If there is boot-file-name option specified, its value is also set in the file field in the DHCPv4 packet. For eRouter1.0 class, the siaddr is always set to 0.0.0.0. That capability is expected to be moved to external hook library that will be dedicated to cable modems. Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario is cable networks. There are two classes of devices: cable modem itself, which should be handled a lease from subnet A and all other devices behind modems that should get a lease from subnet B. That segregation is essential to prevent overly curious users from playing with their cable modems. For details on how to set up class restrictions on subnets, see .

In certain cases it beneficial to restrict access to certain subnets only to clients that belong to a given subnet. For details on client classes, see . This is an extension of a previous example from . Let's assume that the server is connected to a network segment that uses the 192.0.2.0/24 prefix. The Administrator of that network has decided that addresses from range 192.0.2.10 to 192.0.2.20 are going to be managed by the Dhcp4 server. Only clients belonging to client class VENDOR_CLASS_docsis3.0 are allowed to use this subnet. Such a configuration can be achieved in the following way: > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24" > config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ] > config set Dhcp4/subnet4[0]/client-class "VENDOR_CLASS_docsis3.0" > config commit Care should be taken with client classification as it is easy to prevent clients that do not meet class criteria to be denied any service altogether.

As mentioned earlier, b10-dhcp4 can be configured to generate requests to the DHCP-DDNS server to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information: Whether it is a request to add (update) or remove DNS entries Whether the change requests forward DNS updates (A records), reverse DNS updates (PTR records), or both. The FQDN, lease address, and DHCID The parameters for controlling the generation of NCRs for submission to D2 are contained in the "dhcp-ddns" section of the b10-dhcp4 server configuration. The default values for this section appears as follows: > config show Dhcp4/dhcp-ddns Dhcp4/dhcp-ddns/enable-updates true boolean Dhcp4/dhcp-ddns/server-ip "127.0.0.1" string Dhcp4/dhcp-ddns/server-port 53001 integer Dhcp4/dhcp-ddns/sender-ip "" string Dhcp4/dhcp-ddns/sender-port 0 integer Dhcp4/dhcp-ddns/max-queue-size 1024 integer Dhcp4/dhcp-ddns/ncr-protocol "UDP" string Dhcp4/dhcp-ddns/ncr-format "JSON" string Dhcp4/dhcp-ddns/override-no-update false boolean Dhcp4/dhcp-ddns/override-client-update false boolean Dhcp4/dhcp-ddns/replace-client-name false boolean Dhcp4/dhcp-ddns/generated-prefix "myhost" string Dhcp4/dhcp-ddns/qualifying-suffix "example.com" string The "enable-updates" parameter determines whether or not b10-dhcp4 will generate NCRs. By default, this value is false hence DDNS updates are disabled. To enable DDNS updates set this value to true: > config set Dhcp4/dhcp-ddns/enable-updates true > config commit

In order for NCRs to reach the D2 server, b10-dhcp4 must be able to communicate with it. b10-dhcp4 uses the following configuration parameters to control how it communications with D2: server-ip - IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. You may specify either an IPv4 or IPv6 address. server-port - port on which D2 listens for requests. The default value is 53001. sender-ip - IP address which b10-dhcp4 should use to send requests to D2. The default value is blank which instructs b10-dhcp4 to select a suitable address. sender-port - port which b10-dhcp4 should use to send requests to D2. The default value of 0 instructs b10-dhcp4 to select suitable port. ncr-format - Socket protocol use when sending requests to D2. Currently only UDP is supported. TCP may be available in an upcoming release. ncr-protocol - Packet format to use when sending requests to D2. Currently only JSON format is supported. Other formats may be available in future releases. max-queue-size - maximum number of requests allowed to queue waiting to be sent to D2. This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered. If the number of requests queued for transmission reaches this value, DDNS updating will be turned off until the queue backlog has been sufficiently reduced. The intent is allow the b10-dhcp4 server to continue lease operations. The default value is 1024. By default, D2 is assumed to running on the same machine as b10-dhcp4, and all of the default values mentioned above should be sufficient. If, however, D2 has been configured to listen on a different address or port, these values must altered accordingly. For example, if D2 has been configured to listen on 198.162.1.10 port 900, the following commands would be required: > config set Dhcp4/dhcp-ddns/server-ip "198.162.1.10" > config set Dhcp4/dhcp-ddns/server-port 900 > config commit

b10-dhcp4 follows the behavior prescribed for DHCP servers in RFC 4702. It is important to keep in mind that b10-dhcp4 provides the initial decision making of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are the purview of D2 (). This section describes when b10-dhcp4 will generate NCRs and the configuration parameters that can be used to influence this decision. It assumes that the "enable-updates" parameter is true. In general, b10-dhcp4 will generate DDNS update requests when: A new lease is granted in response to a DHCP REQUEST An existing lease is renewed but the FQDN associated with it has changed. An existing lease is released in response to a DHCP RELEASE In the second case, lease renewal, two DDNS requests will be issued: one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN. In the last case, a lease release, a single DDNS request to remove its entries will be made. The decision making involved when granting a new lease (the first case) is more involved and is discussed next. When a new lease is granted, b10-dhcp4 will generate a DDNS update request if the DHCP REQUEST contains either the FQDN option (code 81) or the Host Name option (code 12). If both are present, the server will use the FQDN option. By default b10-dhcp4 will respect the FQDN N and S flags specified by the client as shown in the following table: Client Flags:N-S Client Intent Server Response Server Flags:N-S-O 0-0 Client wants to do forward updates, server should do reverse updates Server generates reverse-only request 1-0-0 0-1 Server should do both forward and reverse updates Server generates request to update both directions 0-1-0 1-0 Client wants no updates done Server does not generate a request 1-0-0 The first row in the table above represents "client delegation". Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverse updates. By default, b10-dhcp4 will honor the client's wishes and generate a DDNS request to D2 to update only reverse DNS data. The parameter, "override-client-update", can be used to instruct the server to override client delegation requests. When this parameter is true, b10-dhcp4 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server's response to the client will be 0-1-1 respectively. (Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by the b10-dhcp4.) To override client delegation, issue the following commands: > config set Dhcp4/dhcp-ddns/override-client-update true > config commit The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter, "override-no-update", can be used to instruct the server to disregard the client's wishes. When this parameter is true, b10-dhcp4 will generate DDNS update request to D2 even if the client requests no updates be done. The N-S-O flags in the server's response to the client will be 0-1-1. To override client delegation, issue the following commands: > config set Dhcp4/dhcp-ddns/override-no-update true > config commit b10-dhcp4 will always generate DDNS update requests if the client request only contains the Host Name option. In addition it will include an FQDN option in the response to the client with the FQDN N-S-O flags set to 0-1-0 respectively. The domain name portion of the FQDN option will be the name submitted to D2 in the DDNS update request.

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. b10-dhcp4 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST. The rules for determining the FQDN option are as follows: If configured to do, so ignore the REQUEST contents and generate a FQDN using a configurable prefix and suffix. If the REQUEST contains the client FQDN option, the candidate name is taken from there, otherwise it is taken from the Host Name option. The candiate name may then be modified: If the candidate name is a fully qualified domain name, use it. If the candidate name is a partial (i.e. unqualified) name then add a configurable suffix to the name and use the result as the FQDN. If the candidate name is a empty, generate a FQDN using a configurable prefix and suffix. To instruct b10-dhcp4 to always generate the FQDN for a client, set the parameter "replace-client-name" to true as follows: > config set Dhcp4/dhcp-ddns/replace-client-name true > config commit The prefix used in the generation of a FQDN is specified by the "generated-prefix" parameter. The default value is "myhost". To alter its value simply set it to the desired string: > config set Dhcp4/dhcp-ddns/generated-prefix "another.host" > config commit The suffix used when generating a FQDN or when qualifying a partial name is specified by the "qualifying-suffix" parameter. The default value is "example.com". To alter its value simply set it to the desired string: > config set Dhcp4/dhcp-ddns/generated-prefix "our.net" > config commit

When generating a name, b10-dhcp4 will construct name of the format: [generated-prefix]-[address-text].[qualifying-suffix]. where address-text is simply the lease IP address converted to a hyphenated string. For example, if lease address is 172.16.1.10 and assuming default values for generated-prefix and qualifying-suffix, the generated FQDN would be: myhost-172-16-1-10.example.com.

The DHCPv4 protocol uses a "server identifier" for clients to be able to discriminate between several servers present on the same link: this value is an IPv4 address of the server. The server chooses the IPv4 address of the interface on which the message from the client (or relay) has been received. A single server instance will use multiple server identifiers if it is receiving queries on multiple interfaces. Currently there is no mechanism to override the default server identifiers by an administrator. In the future, the configuration mechanism will be used to specify the custom server identifier.

In some cases, clients want to obtain configuration from the TFTP server. Although there is a dedicated option for it, some devices may use siaddr field in the DHCPv4 packet for that purpose. That specific field can be configured using next-server directive. It is possible to define it in global scope or for a given subnet only. If both are defined, subnet value takes precedence. The value in subnet can be set to 0.0.0.0, which means that next-server should not be sent. It may also be set to empty string, which means the same as if it was not defined at all - use global value. > config add Dhcp4/next-server > config set Dhcp4/next-server "192.0.2.123" > config commit > config add Dhcp4/subnet[0]/next-server > config set Dhcp4/subnet[0]/next-server "192.0.2.234" > config commit

Original DHCPv4 spec (RFC2131) states that the DHCPv4 server must not send back client-id options when responding to clients. However, in some cases that confused clients that did not have MAC address or client-id. See RFC6842 for details. That behavior has changed with the publication of RFC6842 which updated RFC2131. That update now states that the server must send client-id if client sent it. That is the default behaviour that Kea offers. However, in some cases older devices that do not support RFC6842 may refuse to accept responses that include client-id option. To enable backward compatibility, an optional configuration parameter has been introduced. To configure it, use the following commands: > config add Dhcp4/echo-client-id > config set Dhcp4/echo-client-id False > config commit

The DHCPv4 server differentiates between the directly connected clients, clients trying to renew leases and clients sending their messages through relays. For the directly connected clients the server will check the configuration of the interface on which the message has been received, and if the server configuration doesn't match any configured subnet the message is discarded. Assuming that the server's interface is configured with the 192.0.2.3 IPv4 address, the server will only process messages received through this interface from the directly connected client, if there is a subnet configured, to which this IPv4 address belongs, e.g. 192.0.2.0/24. The server will use this subnet to assign IPv4 address for the client. The rule above does not apply when the client unicasts its message, i.e. is trying to renew its lease. Such message is accepted through any interface. The renewing client sets ciaddr to the currently used IPv4 address. The server uses this address to select the subnet for the client (in particular, to extend the lease using this address). If the message is relayed it is accepted through any interface. The giaddr set by the relay agent is used to select the subnet for the client. It is also possible to specify a relay IPv4 address for a given subnet. It can be used to match incoming packets into a subnet in uncommon configurations, e.g. shared subnets. See for details. The subnet selection mechanism described in this section is based on the assumption that client classification is not used. The classification mechanism alters the way in which subnet is selected for the client, depending on the classes that the client belongs to.

The relay has to have an interface connected to the link on which the clients are being configured. Typically the relay has an IPv4 address configured on that interface that belongs to the subnet that the server will assign addresses from. In such typical case, the server is able to use IPv4 address inserted by the relay (in GIADDR field of the DHCPv4 packet) to select appropriate subnet. However, that is not always the case. In certain uncommon, but valid deployments, the relay address may not match the subnet. This usually means that there is more than one subnet allocated for a given link. Two most common examples where this is the case are long lasting network renumbering (where both old and new address space is still being used) and a cable network. In a cable network both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such case, the DHCPv4 server needs additional information (IPv4 address of the relay) to properly select an appropriate subnet. The following example assumes that there is a subnet 192.0.2.0/24 that is accessible via relay that uses 10.0.0.1 as its IPv4 address. The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 192.0.2.0/24 subnet. It will also select that subnet for a relay with address 10.0.0.1. > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[0]/subnet "192.0.2.0/24" > config set Dhcp4/subnet4[0]/pool [ "192.0.2.10 - 192.0.2.20" ] > config set Dhcp4/subnet4[0]/relay/ip-address "10.0.0.1" > config commit

In certain cases, it is useful to mix relay address information, introduced in with client classification, explained in . One specific example is cable network, where typically modems get addresses from a different subnet than all devices connected behind them. Let's assume that there is one CMTS (Cable Modem Termination System) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 10.1.1.0/24 subnet, while everything connected behind modems should get addresses from another subnet (192.0.2.0/24). The CMTS that acts as a relay an uses address 10.1.1.1. The following configuration can serve that configuration: > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[0]/subnet "10.1.1.0/24" > config set Dhcp4/subnet4[0]/pool [ "10.1.1.2 - 10.1.1.20" ] > config set Dhcp4/subnet4[0]/client-class "docsis3.0" > config set Dhcp4/subnet4[0]/relay/ip-address "10.1.1.1" > config add Dhcp4/subnet4 > config set Dhcp4/subnet4[1]/subnet "192.0.2.0/24" > config set Dhcp4/subnet4[1]/pool [ "192.0.2.10 - 192.0.2.20" ] > config set Dhcp4/subnet4[1]/relay/ip-address "10.1.1.1" > config commit

The following standards and draft standards are currently supported: RFC 2131: Supported messages are DISCOVER, OFFER, REQUEST, RELEASE, ACK, and NAK. RFC 2132: Supported options are: PAD (0), END(255), Message Type(53), DHCP Server Identifier (54), Domain Name (15), DNS Servers (6), IP Address Lease Time (51), Subnet mask (1), and Routers (3). RFC 3046: Relay Agent Information option is supported. RFC 3925: Vendor-Identifying Vendor Class and Vendor-Identifying Vendor-Specific Information option are supported. RFC 6842: Server by default sends back client-id option. That capability may be disabled. See for details.

These are the current limitations of the DHCPv4 server software. Most of them are reflections of the current stage of development and should be treated as not implemented yet, rather than actual limitations. Removal of a subnet during server reconfiguration may cause renumbering of auto-generated subnet identifiers, as described in section . BOOTP (RFC 951) is not supported. Raw sockets operation is working on Linux only. See for details. The DHCPv4 server does not verify that assigned address is unused. According to RFC 2131, the allocating server should verify that address is not used by sending ICMP echo request. Address duplication report (DECLINE) is not supported yet. The server doesn't act upon expired leases. In particular, when a lease expires, the server doesn't request the removal of the DNS records associated with it.

b10-dhcp6 is the Kea DHCPv6 server and is configured through the bindctl program. After starting bind10 and starting bindctl, the first step in configuring the server is to add b10-dhcp6 to the list of running services. > config add Init/components b10-dhcp6 > config set Init/components/b10-dhcp6/kind dispensable > config commit To remove b10-dhcp6 from the set of running services, the b10-dhcp6 is removed from list of Init components: > config remove Init/components b10-dhcp6 > config commit Note that the server was only removed from the list, so BIND10 will not restart it, but the server itself is still running. Hence it is usually desired to stop it: > Dhcp6 shutdown During start-up the server will detect available network interfaces and will attempt to open UDP sockets on all interfaces that are up, running, are not loopback, are multicast-capable, and have IPv6 address assigned. It will then listen to incoming traffic.

Once the server has been started, it can be configured. To view the current configuration, use the following command in bindctl: > config show Dhcp6 When starting the Dhcp6 daemon for the first time, the default configuration will be available. It will look similar to this: > config show Dhcp6 Dhcp6/hooks-libraries [] list (default) Dhcp6/interfaces/ list (default) Dhcp6/renew-timer 1000 integer (default) Dhcp6/rebind-timer 2000 integer (default) Dhcp6/preferred-lifetime 3000 integer (default) Dhcp6/valid-lifetime 4000 integer (default) Dhcp6/option-def [] list (default) Dhcp6/option-data [] list (default) Dhcp6/lease-database/type "" string (default) Dhcp6/lease-database/name "" string (default) Dhcp6/lease-database/user "" string (default) Dhcp6/lease-database/host "" string (default) Dhcp6/lease-database/password "" string (default) Dhcp6/subnet6/ list Dhcp6/dhcp-ddns/enable-updates true boolean Dhcp6/dhcp-ddns/server-ip "127.0.0.1" string Dhcp6/dhcp-ddns/server-port 53001 integer Dhcp6/dhcp-ddns/sender-ip "" string Dhcp6/dhcp-ddns/sender-port 0 integer Dhcp6/dhcp-ddns/max-queue-size 1024 integer Dhcp6/dhcp-ddns/ncr-protocol "UDP" string Dhcp6/dhcp-ddns/ncr-format "JSON" string Dhcp6/dhcp-ddns/always-include-fqdn false boolean Dhcp6/dhcp-ddns/override-no-update false boolean Dhcp6/dhcp-ddns/override-client-update false boolean Dhcp6/dhcp-ddns/replace-client-name false boolean Dhcp6/dhcp-ddns/generated-prefix "myhost" string Dhcp6/dhcp-ddns/qualifying-suffix "example.com" string To change one of the parameters, simply follow the usual bindctl procedure. For example, to make the leases longer, change their valid-lifetime parameter: > config set Dhcp6/valid-lifetime 7200 > config commit Most Dhcp6 parameters are of global scope and apply to all defined subnets, unless they are overridden on a per-subnet basis. With this version of Kea, there are a number of known limitations and problems in the DHCPv6 server. See .

The server is able to store lease data in different repositories. Larger deployments may elect to store leases in a database. describes one way to do it. By default, the server will use a CSV file rather than a database to store lease information. One of the advantages of using a file is that it eliminates dependency on third party database software. The configuration of the file backend (Memfile) is controlled through the Dhcp6/lease-database parameters. When default parameters are left, the Memfile backend will write leases to a disk in the [bind10-install-dir]/var/bind10/kea-leases6.csv. It is possible to alter the default location of the lease file. The following configuration: > config set Dhcp4/lease-database/type "memfile" > config set Dhcp4/lease-database/persist true > config set Dhcp4/lease-database/leasefile "/tmp/kea-leases6.csv" > config commit will change the default location of the lease file to /tmp/kea-leases6.csv. The "persist" parameter controls whether the leases are written to disk. It is strongly recommended that this parameter is set to "true" at all times during the normal operation of the server.

All leases issued by the server are stored in the lease database. Currently there are 3 database backends available: MySQL, PostgreSQL and memfile. The server comes with an in-memory database ("memfile") configured as the default database. This is used for internal testing and is not supported. In addition, it does not store lease information on disk: lease information will be lost if the server is restarted. , and so the server must be configured to access the correct database with the appropriate credentials. Database access information must be configured for the DHCPv6 server, even if it has already been configured for the DHCPv4 server. The servers store their information independently, so each server can use a separate database or both servers can use the same database. Database configuration is controlled through the Dhcp6/lease-database parameters. The type of the database must be set to "mysql", "postgresql" or "memfile": > config set Dhcp6/lease-database/type "mysql" Next, the name of the database is to hold the leases must be set: this is the name used when the lease database was created (see or ). > config set Dhcp6/lease-database/name "database-name" If the database is located on a different system to the DHCPv6 server, the database host name must also be specified (although note that this configuration may have a severe impact on server performance): > config set Dhcp6/lease-database/host "remote-host-name" The usual state of affairs will be to have the database on the same machine as the DHCPv6 server. In this case, set the value to the empty string (this is the default): > config set Dhcp6/lease-database/host "" Finally, the credentials of the account under which the server will access the database should be set: > config set Dhcp6/lease-database/user "user-name" > config set Dhcp6/lease-database/password "password" If there is no password to the account, set the password to the empty string "". (This is also the default.) The password is echoed when entered and is stored in clear text in the configuration database. Improved password security will be added in a future version of Kea.

When DHCPv6 server starts up, by default it will listen to the DHCP traffic and respond to it on all interfaces detected during startup. However, in many cases it is desired to configure the server to listen and respond on selected interfaces only. The sample commands in this section show how to make interface selection using bindctl. The default configuration can be presented with the following command: > config show Dhcp6/interfaces Dhcp6/interfaces[0] "*" string An asterisk sign plays a role of the wildcard and means "listen on all interfaces". In order to override the default configuration, the existing entry can be replaced with the actual interface name: > config set Dhcp6/interfaces[0] eth1 > config commit Other interface names can be added on one-by-one basis: > config add Dhcp6/interfaces eth2 > config commit Configuration will now contain two interfaces which can be presented as follows: > config show Dhcp6/interfaces Dhcp6/interfaces[0] "eth1" string Dhcp6/interfaces[1] "eth2" string When configuration gets committed, the server will start to listen on eth1 and eth2 interfaces only. It is possible to use wildcard interface name (asterisk) concurrently with explicit interface names: > config add Dhcp6/interfaces * > config commit This will result in the following configuration: > config show Dhcp6/interfaces Dhcp6/interfaces[0] "eth1" string Dhcp6/interfaces[1] "eth2" string Dhcp6/interfaces[2] "*" string The presence of the wildcard name implies that server will listen on all interfaces. In order to fall back to the previous configuration when server listens on eth1 and eth2: > config remove Dhcp6/interfaces[2] > config commit

Subnet identifier is a unique number associated with a particular subnet. In principle, it is used to associate clients' leases with respective subnets. When subnet identifier is not specified for a subnet being configured, it will be automatically assigned by the configuration mechanism. The identifiers are assigned from 1 and are monotonically increased for each subsequent subnet: 1, 2, 3 .... If there are multiple subnets configured with auto-generated identifiers and one of them is removed, the subnet identifiers may be renumbered. For example: if there are 4 subnets and 3rd is removed the last subnet will be assigned identifier that the 3rd subnet had before removal. As a result, the leases stored in the lease database for subnet 3 are now associated with the subnet 4, which may have unexpected consequences. In the future it is planned to implement the mechanism to preserve auto-generated subnet ids upon removal of one of the subnets. Currently, the only remedy for this issue is to manually specify the unique subnet identifier for each subnet. The following configuration: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64" > config set Dhcp6/subnet6[0]/id 1024 > config commit will assign the arbitrary subnet identifier to the newly configured subnet. This identifier will not change for this subnet until "id" parameter is removed or set to 0. The value of 0 forces auto-generation of subnet identifier.

When DHCPv6 server starts up, by default it listens to the DHCP traffic sent to multicast address ff02::1:2 on each interface that it is configured to listen on (see ). In some cases it is useful to configure a server to handle incoming traffic sent to the global unicast addresses as well. The most common reason for that is to have relays send their traffic to the server directly. To configure server to listen on specific unicast address, a notation to specify interfaces has been extended. Interface name can be optionally followed by a slash, followed by global unicast address that server should listen on. That will be done in addition to normal link-local binding + listening on ff02::1:2 address. The sample commands listed below show how to listen on 2001:db8::1 (a global address) configured on the eth1 interface. > config set Dhcp6/interfaces[0] eth1/2001:db8::1 > config commit When configuration gets committed, the server will start to listen on eth1 on link-local address, multicast group (ff02::1:2) and 2001:db8::1. It is possible to mix interface names, wildcards and interface name/addresses on the Dhcp6/interface list. It is not possible to specify more than one unicast address on a given interface. Care should be taken to specify proper unicast addresses. The server will attempt to bind to those addresses specified, without any additional checks. That approach is selected on purpose, so in the software can be used to communicate over uncommon addresses if the administrator desires so.

The essential role of a DHCPv6 server is address assignment. For this, the server has to be configured with at least one subnet and one pool of dynamic addresses to be managed. For example, assume that the server is connected to a network segment that uses the 2001:db8:1::/64 prefix. The Administrator of that network has decided that addresses from range 2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the Dhcp6 server. Such a configuration can be achieved in the following way: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64" > config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::0 - 2001:db8:1::ffff" ] > config commit Note that subnet is defined as a simple string, but the pool parameter is actually a list of pools: for this reason, the pool definition is enclosed in square brackets, even though only one range of addresses is specified. It is possible to define more than one pool in a subnet: continuing the previous example, further assume that 2001:db8:1:0:5::/80 should be also be managed by the server. It could be written as 2001:db8:1:0:5:: to 2001:db8:1::5:ffff:ffff:ffff, but typing so many 'f's is cumbersome. It can be expressed more simply as 2001:db8:1:0:5::/80. Both formats are supported by Dhcp6 and can be mixed in the pool list. For example, one could define the following pools: > config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::1 - 2001:db8:1::ffff", "2001:db8:1:0:5::/80" ] > config commit The number of pools is not limited, but for performance reasons it is recommended to use as few as possible. The server may be configured to serve more than one subnet. To add a second subnet, use a command similar to the following: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[1]/subnet "2001:db8:beef::/48" > config set Dhcp6/subnet6[1]/pool [ "2001:db8:beef::/48" ] > config commit Arrays are counted from 0. subnet[0] refers to the subnet defined in the previous example. The config add Dhcp6/subnet6 command adds another (second) subnet. It can be referred to as Dhcp6/subnet6[1]. In this example, we allow server to dynamically assign all addresses available in the whole subnet. Although very wasteful, it is certainly a valid configuration to dedicate the whole /48 subnet for that purpose. When configuring a DHCPv6 server using prefix/length notation, please pay attention to the boundary values. When specifying that the server should use a given pool, it will be able to allocate also first (typically network address) address from that pool. For example for pool 2001:db8::/64 the 2001:db8:: address may be assigned as well. If you want to avoid this, please use the "min-max" notation.

Subnets may also be configured to delegate address prefixes.... A subnet may have one or more prefix delegation pools. Each pool has a prefixed address, which is specified as a prefix and a prefix length, as well as a delegated prefix length. A sample configuration is shown below: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64" > config show Dhcp6/subnet6[0] > config add Dhcp6/subnet6[0]/pd-pools > config set Dhcp6/subnet6[0]/pd-pools[0]/prefix "2001:db8:1::" > config set Dhcp6/subnet6[0]/pd-pools[0]/prefix-len 64 > config set Dhcp6/subnet6[0]/pd-pools[0]/delegated-len 96 > config commit

One of the major features of DHCPv6 server is to provide configuration options to clients. Although there are several options that require special behavior, most options are sent by the server only if the client explicitly requested them. The following example shows how to configure DNS servers, which is one of the most frequently used options. Numbers in the first column are added for easier reference and will not appear on screen. Options specified in this way are considered global and apply to all configured subnets. 1. > config add Dhcp6/option-data 2. > config set Dhcp6/option-data[0]/name "dns-servers" 3. > config set Dhcp6/option-data[0]/code 23 4. > config set Dhcp6/option-data[0]/space "dhcp6" 5. > config set Dhcp6/option-data[0]/csv-format true 6. > config set Dhcp6/option-data[0]/data "2001:db8::cafe, 2001:db8::babe" 7. > config commit The first line creates new entry in option-data table. It contains information on all global options that the server is supposed to configure in all subnets. The second line specifies option name. For a complete list of currently supported names, see . The third line specifies option code, which must match one of the values from that list. Line 4 specifies option space, which must always be set to "dhcp6" as these are standard DHCPv6 options. For other name spaces, including custom option spaces, see . The fifth line specifies the format in which the data will be entered: use of CSV (comma separated values) is recommended. The sixth line gives the actual value to be sent to clients. Data is specified as a normal text, with values separated by commas if more than one value is allowed. Options can also be configured as hexadecimal values. If csv-format is set to false, the option data must be specified as a string of hexadecimal numbers. The following commands configure the DNS-SERVERS option for all subnets with the following addresses: 2001:db8:1::cafe and 2001:db8:1::babe. > config add Dhcp6/option-data > config set Dhcp6/option-data[0]/name "dns-servers" > config set Dhcp6/option-data[0]/code 23 > config set Dhcp6/option-data[0]/space "dhcp6" > config set Dhcp6/option-data[0]/csv-format false > config set Dhcp6/option-data[0]/data "2001 0DB8 0001 0000 0000 0000 0000 CAFE 2001 0DB8 0001 0000 0000 0000 0000 BABE" > config commit (The value for the setting of the "data" element is split across two lines in this document for clarity: when entering the command, the whole string should be entered on the same line.) It is possible to override options on a per-subnet basis. If clients connected to most of your subnets are expected to get the same values of a given option, you should use global options: you can then override specific values for a small number of subnets. On the other hand, if you use different values in each subnet, it does not make sense to specify global option values (Dhcp6/option-data), rather you should set only subnet-specific values (Dhcp6/subnet[X]/option-data[Y]). The following commands override the global DNS servers option for a particular subnet, setting a single DNS server with address 2001:db8:1::3. > config add Dhcp6/subnet6[0]/option-data > config set Dhcp6/subnet6[0]/option-data[0]/name "dns-servers" > config set Dhcp6/subnet6[0]/option-data[0]/code 23 > config set Dhcp6/subnet6[0]/option-data[0]/space "dhcp6" > config set Dhcp6/subnet6[0]/option-data[0]/csv-format true > config set Dhcp6/subnet6[0]/option-data[0]/data "2001:db8:1::3" > config commit In future versions of BIND 10 DHCP, it will not be necessary to specify option code, space and csv-format fields, as those fields will be set automatically. The currently supported standard DHCPv6 options are listed in . The "Name" and "Code" are the values that should be used as a name in the option-data structures. "Type" designates the format of the data: the meanings of the various types is given in . Some options are designated as arrays, which means that more than one value is allowed in such an option. For example the option dns-servers allows the specification of more than one IPv6 address, so allowing clients to obtain the the addresses of multiple DNS servers. The describes the configuration syntax to create custom option definitions (formats). It is generally not allowed to create custom definitions for standard options, even if the definition being created matches the actual option format defined in the RFCs. There is an exception from this rule for standard options for which Kea does not provide a definition yet. In order to use such options, a server administrator must create a definition as described in in the 'dhcp6' option space. This definition should match the option format described in the relevant RFC but configuration mechanism would allow any option format as it has no means to validate it at the moment. NameCodeTypeArray?preference7uint8falsesip-server-dns21fqdntruesip-server-addr22ipv6-addresstruedns-servers23ipv6-addresstruedomain-search24fqdntruenis-servers27ipv6-addresstruenisp-servers28ipv6-addresstruenis-domain-name29fqdntruenisp-domain-name30fqdntruesntp-servers31ipv6-addresstrueinformation-refresh-time32uint32falsebcmcs-server-dns33fqdntruebcmcs-server-addr34ipv6-addresstruegeoconf-civic36recordfalseremote-id37recordfalsesubscriber-id38binaryfalseclient-fqdn39recordfalsepana-agent40ipv6-addresstruenew-posix-timezone41stringfalsenew-tzdb-timezone42stringfalseero43uint16truelq-query44recordfalseclient-data45emptyfalseclt-time46uint32falselq-relay-data47recordfalselq-client-link48ipv6-addresstrue

It is also possible to define options other than the standard ones. Assume that we want to define a new DHCPv6 option called "foo" which will have code 100 and will convey a single unsigned 32 bit integer value. We can define such an option by using the following commands: > config add Dhcp6/option-def > config set Dhcp6/option-def[0]/name "foo" > config set Dhcp6/option-def[0]/code 100 > config set Dhcp6/option-def[0]/type "uint32" > config set Dhcp6/option-def[0]/array false > config set Dhcp6/option-def[0]/record-types "" > config set Dhcp6/option-def[0]/space "dhcp6" > config set Dhcp6/option-def[0]/encapsulate "" > config commit The "false" value of the "array" parameter determines that the option does NOT comprise an array of "uint32" values but rather a single value. Two other parameters have been left blank: "record-types" and "encapsulate". The former specifies the comma separated list of option data fields if the option comprises a record of data fields. The "record-fields" value should be non-empty if the "type" is set to "record". Otherwise it must be left blank. The latter parameter specifies the name of the option space being encapsulated by the particular option. If the particular option does not encapsulate any option space it should be left blank. Note that the above set of comments define the format of the new option and do not set its values. Once the new option format is defined, its value is set in the same way as for a standard option. For example the following commands set a global value that applies to all subnets. > config add Dhcp6/option-data > config set Dhcp6/option-data[0]/name "foo" > config set Dhcp6/option-data[0]/code 100 > config set Dhcp6/option-data[0]/space "dhcp6" > config set Dhcp6/option-data[0]/csv-format true > config set Dhcp6/option-data[0]/data "12345" > config commit New options can take more complex forms than simple use of primitives (uint8, string, ipv6-address etc): it is possible to define an option comprising a number of existing primitives. Assume we want to define a new option that will consist of an IPv6 address, followed by an unsigned 16 bit integer, followed by a boolean value, followed by a text string. Such an option could be defined in the following way: > config add Dhcp6/option-def > config set Dhcp6/option-def[0]/name "bar" > config set Dhcp6/option-def[0]/code 101 > config set Dhcp6/option-def[0]/space "dhcp6" > config set Dhcp6/option-def[0]/type "record" > config set Dhcp6/option-def[0]/array false > config set Dhcp6/option-def[0]/record-types "ipv6-address, uint16, boolean, string" > config set Dhcp6/option-def[0]/encapsulate "" The "type" is set to "record" to indicate that the option contains multiple values of different types. These types are given as a comma-separated list in the "record-types" field and should be those listed in . The values of the option are set as follows: > config add Dhcp6/option-data > config set Dhcp6/option-data[0]/name "bar" > config set Dhcp6/option-data[0]/space "dhcp6" > config set Dhcp6/option-data[0]/code 101 > config set Dhcp6/option-data[0]/csv-format true > config set Dhcp6/option-data[0]/data "2001:db8:1::10, 123, false, Hello World" > config commit "csv-format" is set "true" to indicate that the "data" field comprises a command-separated list of values. The values in the "data" must correspond to the types set in the "record-types" field of the option definition. It is recommended that boolean values are specified using "true" and "false" strings. This helps to prevent errors when typing multiple comma separated values, as it make it easier to identify the type of the value being typed, and compare it with the order of data fields. Nevertheless, it is possible to use integer values: "1" and "0", instead of "true" and "false" accordingly. If other integer value is specified, the configuration is rejected.

Currently there are three option spaces defined: dhcp4 (to be used in DHCPv4 daemon) and dhcp6 (for the DHCPv6 daemon); there is also vendor-opts-space, which is empty by default, but options can be defined in it. Those options are called vendor-specific information options. The following examples show how to define an option "foo" with code 1 that consists of an IPv6 address, an unsigned 16 bit integer and a string. The "foo" option is conveyed in a vendor specific information option. This option comprises a single uint32 value that is set to "12345". The sub-option "foo" follows the data field holding this value. > config add Dhcp6/option-def > config set Dhcp6/option-def[0]/name "foo" > config set Dhcp6/option-def[0]/code 1 > config set Dhcp6/option-def[0]/space "vendor-opts-space" > config set Dhcp6/option-def[0]/type "record" > config set Dhcp6/option-def[0]/array false > config set Dhcp6/option-def[0]/record-types "ipv6-address, uint16, string" > config set Dhcp6/option-def[0]/encapsulates "" > config commit (Note that the option space is set to "vendor-opts-space".) Once the option format is defined, the next step is to define actual values for that option: > config add Dhcp6/option-data > config set Dhcp6/option-data[0]/name "foo" > config set Dhcp6/option-data[0]/space "vendor-opts-space" > config set Dhcp6/option-data[0]/code 1 > config set Dhcp6/option-data[0]/csv-format true > config set Dhcp6/option-data[0]/data "2001:db8:1::10, 123, Hello World" > config commit We should also define values for the vendor-opts, that will convey our option foo. > config add Dhcp6/option-data > config set Dhcp6/option-data[1]/name "vendor-opts" > config set Dhcp6/option-data[1]/space "dhcp6" > config set Dhcp6/option-data[1]/code 17 > config set Dhcp6/option-data[1]/csv-format true > config set Dhcp6/option-data[1]/data "12345" > config commit

It is sometimes useful to define completely new option spaces. This is useful if the user wants his new option to convey sub-options that use separate numbering scheme, for example sub-options with codes 1 and 2. Those option codes conflict with standard DHCPv6 options, so a separate option space must be defined. Note that it is not required to create new option space when defining sub-options for a standard option because it is by default created if the standard option is meant to convey any sub-options (see ). Assume that we want to have a DHCPv6 option called "container" with code 102 that conveys two sub-options with codes 1 and 2. First we need to define the new sub-options: > config add Dhcp6/option-def > config set Dhcp6/option-def[0]/name "subopt1" > config set Dhcp6/option-def[0]/code 1 > config set Dhcp6/option-def[0]/space "isc" > config set Dhcp6/option-def[0]/type "ipv6-address" > config set Dhcp6/option-def[0]/record-types "" > config set Dhcp6/option-def[0]/array false > config set Dhcp6/option-def[0]/encapsulate "" > config commit > > config add Dhcp6/option-def > config set Dhcp6/option-def[1]/name "subopt2" > config set Dhcp6/option-def[1]/code 2 > config set Dhcp6/option-def[1]/space "isc" > config set Dhcp6/option-def[1]/type "string" > config set Dhcp6/option-def[1]/record-types "" > config set Dhcp6/option-def[1]/array false > config set Dhcp6/option-def[1]/encapsulate "" > config commit Note that we have defined the options to belong to a new option space (in this case, "isc"). The next step is to define a regular DHCPv6 option and specify that it should include options from the isc option space: > config add Dhcp6/option-def > config set Dhcp6/option-def[2]/name "container" > config set Dhcp6/option-def[2]/code 102 > config set Dhcp6/option-def[2]/space "dhcp6" > config set Dhcp6/option-def[2]/type "empty" > config set Dhcp6/option-def[2]/array false > config set Dhcp6/option-def[2]/record-types "" > config set Dhcp6/option-def[2]/encapsulate "isc" > config commit The name of the option space in which the sub-options are defined is set in the "encapsulate" field. The "type" field is set to "empty" which imposes that this option does not carry any data other than sub-options. Finally, we can set values for the new options: > config add Dhcp6/option-data > config set Dhcp6/option-data[0]/name "subopt1" > config set Dhcp6/option-data[0]/space "isc" > config set Dhcp6/option-data[0]/code 1 > config set Dhcp6/option-data[0]/csv-format true > config set Dhcp6/option-data[0]/data "2001:db8::abcd" > config commit > > config add Dhcp6/option-data > config set Dhcp6/option-data[1]/name "subopt2" > config set Dhcp6/option-data[1]/space "isc" > config set Dhcp6/option-data[1]/code 2 > config set Dhcp6/option-data[1]/csv-format true > config set Dhcp6/option-data[1]/data "Hello world" > config commit > > config add Dhcp6/option-data > config set Dhcp6/option-data[2]/name "container" > config set Dhcp6/option-data[2]/space "dhcp6" > config set Dhcp6/option-data[2]/code 102 > config set Dhcp6/option-data[2]/csv-format true > config set Dhcp6/option-data[2]/data "" > config commit Even though the "container" option does not carry any data except sub-options, the "data" field must be explicitly set to an empty value. This is required because in the current version of BIND 10 DHCP, the default configuration values are not propagated to the configuration parsers: if the "data" is not set the parser will assume that this parameter is not specified and an error will be reported. Note that it is possible to create an option which carries some data in addition to the sub-options defined in the encapsulated option space. For example, if the "container" option from the previous example was required to carry an uint16 value as well as the sub-options, the "type" value would have to be set to "uint16" in the option definition. (Such an option would then have the following data structure: DHCP header, uint16 value, sub-options.) The value specified with the "data" parameter - which should be a valid integer enclosed in quotes, e.g. "123" - would then be assigned to the uint16 field in the "container" option.

The DHCPv6 server may receive requests from local (connected to the same subnet as the server) and remote (connecting via relays) clients. As server may have many subnet configurations defined, it must select appropriate subnet for a given request. The server can not assume which of configured subnets are local. It is possible in IPv4, where there is reasonable expectation that the server will have a (global) IPv4 address configured on the interface, and can use that information to detect whether a subnet is local or not. That assumption is not true in IPv6, as the DHCPv6 must be able to operate with having link-local addresses only. Therefore an optional "interface" parameter is available within a subnet definition to designate that a given subnet is local, i.e. reachable directly over specified interface. For example the server that is intended to serve a local subnet over eth0 may be configured as follows: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[1]/subnet "2001:db8:beef::/48" > config set Dhcp6/subnet6[1]/pool [ "2001:db8:beef::/48" ] > config set Dhcp6/subnet6[1]/interface "eth0" > config commit

A DHCPv6 server with multiple subnets defined must select the appropriate subnet when it receives a request from client. For clients connected via relays, two mechanisms are used: The first uses the linkaddr field in the RELAY_FORW message. The name of this field is somewhat misleading in that it does not contain a link-layer address: instead, it holds an address (typically a global address) that is used to identify a link. The DHCPv6 server checks if the address belongs to a defined subnet and, if it does, that subnet is selected for the client's request. The second mechanism is based on interface-id options. While forwarding a client's message, relays may insert an interface-id option into the message that identifies the interface on the relay that received the message. (Some relays allow configuration of that parameter, but it is sometimes hardcoded and may range from the very simple (e.g. "vlan100") to the very cryptic: one example seen on real hardware was "ISAM144|299|ipv6|nt:vp:1:110"). The server can use this information to select the appropriate subnet. The information is also returned to the relay which then knows the interface to use to transmit the response to the client. In order for this to work successfully, the relay interface IDs must be unique within the network and the server configuration must match those values. When configuring the DHCPv6 server, it should be noted that two similarly-named parameters can be configured for a subnet: "interface" defines which local network interface can be used to access a given subnet. "interface-id" specifies the content of the interface-id option used by relays to identify the interface on the relay to which the response packet is sent. The two are mutually exclusive: a subnet cannot be both reachable locally (direct traffic) and via relays (remote traffic). Specifying both is a configuration error and the DHCPv6 server will refuse such a configuration. To specify interface-id with value "vlan123", the following commands can be used: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:beef::/48" > config set Dhcp6/subnet6[0]/pool [ "2001:db8:beef::/48" ] > config set Dhcp6/subnet6[0]/interface-id "vland123" > config commit

DHCPv6 server has been extended to support limited client classification. Although the current capability is modest, it is expected to be expanded in the future. It is envisaged that the majority of client classification extensions will be using hooks extensions. In certain cases it is useful to differentiate between different types of clients and treat them differently. The process of doing classification is conducted in two steps. The first step is to assess incoming packet and assign it to zero or more classes. This classification is currently simple, but is expected to grow in capability soon. Currently the server checks whether incoming packet has vendor class option (16). If it has, content of that option is prepended with "VENDOR_CLASS_" interpreted as a class. For example, modern cable modems will send this option with value "docsis3.0" and as a result the packet will belong to class "VENDOR_CLASS_docsis3.0". It is envisaged that the client classification will be used for changing behavior of almost any part of the DHCP engine processing, including assigning leases from different pools, assigning different option (or different values of the same options) etc. For now, there is only one mechanism that is taking advantage of client classification: subnet selection. Kea can be instructed to limit access to given subnets based on class information. This is particularly useful for cases where two types of devices share the same link and are expected to be served from two different subnets. The primary use case for such a scenario are cable networks. There are two classes of devices: cable modem itself, which should be handled a lease from subnet A and all other devices behind modems that should get a lease from subnet B. That segregation is essential to prevent overly curious users from playing with their cable modems. For details on how to set up class restrictions on subnets, see .

In certain cases it beneficial to restrict access to certains subnets only to clients that belong to a given subnet. For details on client classes, see . This is an extension of a previous example from . Let's assume that the server is connected to a network segment that uses the 2001:db8:1::/64 prefix. The Administrator of that network has decided that addresses from range 2001:db8:1::1 to 2001:db8:1::ffff are going to be managed by the Dhcp6 server. Only clients belonging to the eRouter1.0 client class are allowed to use that pool. Such a configuration can be achieved in the following way: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64" > config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::0 - 2001:db8:1::ffff" ] > config set Dhcp6/subnet6[0]/client-class "eRouter1.0" > config commit Care should be taken with client classification as it is easy to prevent clients that do not meet class criteria to be denied any service altogether.

As mentioned earlier, b10-dhcp6 can be configured to generate requests to the DHCP-DDNS server (referred to here as the "D2" server) to update DNS entries. These requests are known as NameChangeRequests or NCRs. Each NCR contains the following information: Whether it is a request to add (update) or remove DNS entries Whether the change requests forward DNS updates (AAAA records), reverse DNS updates (PTR records), or both. The FQDN, lease address, and DHCID The parameters controlling the generation of NCRs for submission to D2 are contained in the "dhcp-ddns" section of b10-dhcp6 configuration. The default values for this section appears as follows: > config show Dhcp6/dhcp-ddns Dhcp6/dhcp-ddns/enable-updates true boolean Dhcp6/dhcp-ddns/server-ip "127.0.0.1" string Dhcp6/dhcp-ddns/server-port 53001 integer Dhcp6/dhcp-ddns/sender-ip "" string Dhcp6/dhcp-ddns/sender-port 0 integer Dhcp6/dhcp-ddns/max-queue-size 1024 integer Dhcp6/dhcp-ddns/ncr-protocol "UDP" string Dhcp6/dhcp-ddns/ncr-format "JSON" string Dhcp6/dhcp-ddns/override-no-update false boolean Dhcp6/dhcp-ddns/override-client-update false boolean Dhcp6/dhcp-ddns/replace-client-name false boolean Dhcp6/dhcp-ddns/generated-prefix "myhost" string Dhcp6/dhcp-ddns/qualifying-suffix "example.com" string The "enable-updates" parameter determines whether or not b10-dhcp6 will generate NCRs. By default, this value is false hence DDNS updates are disabled. To enable DDNS updates set this value to true as follows: > config set Dhcp6/dhcp-ddns/enable-updates true > config commit

In order for NCRs to reach the D2 server, b10-dhcp6 must be able to communicate with it. b10-dhcp6 uses the following configuration parameters to control how it communications with D2: server-ip - IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. You may specify either an IPv4 or IPv6 address. server-port - port on which D2 listens for requests. The default value is 53001. sender-ip - IP address which b10-dhcp6 should use to send requests to D2. The default value is blank which instructs b10-dhcp6 to select a suitable address. sender-port - port which b10-dhcp6 should use to send requests to D2. The default value of 0 instructs b10-dhcp6 to select suitable port. ncr-format - Socket protocol use when sending requests to D2. Currently only UDP is supported. TCP may be available in an upcoming release. ncr-protocol - Packet format to use when sending requests to D2. Currently only JSON format is supported. Other formats may be available in future releases. max-queue-size - maximum number of requests allowed to queue waiting to be sent to D2. This value guards against requests accumulating uncontrollably if they are being generated faster than they can be delivered. If the number of requests queued for transmission reaches this value, DDNS updating will be turned off until the queue backlog has been sufficiently reduced. The intent is allow b10-dhcp6 to continue lease operations. The default value is 1024. By default, D2 is assumed to running on the same machine as b10-dhcp6, and all of the default values mentioned above should be sufficient. If, however, D2 has been configured to listen on a different address or port, these values must altered accordingly. For example, if D2 has been configured to listen on 3001::5 port 900, the following commands would be required: > config set Dhcp6/dhcp-ddns/server-ip "3001::5" > config set Dhcp6/dhcp-ddns/server-port 900 > config commit

b10-dhcp6 follows the behavior prescribed for DHCP servers in RFC 4704. It is important to keep in mind that b10-dhcp6 provides the initial decision making of when and what to update and forwards that information to D2 in the form of NCRs. Carrying out the actual DNS updates and dealing with such things as conflict resolution are the purview of D2 (). This section describes when b10-dhcp6 will generate NCRs and the configuration parameters that can be used to influence this decision. It assumes that the "enable-updates" parameter is true. Currently the interface between b10-dhcp6 and D2 only supports requests which update DNS entries for a single IP address. If a lease grants more than one address, b10-dhcp6 will create the DDNS update request for only the first of these addresses. Support for multiple address mappings may be provided in a future release. In general, b10-dhcp6 will generate DDNS update requests when: A new lease is granted in response to a DHCP REQUEST An existing lease is renewed but the FQDN associated with it has changed. An existing lease is released in response to a DHCP RELEASE In the second case, lease renewal, two DDNS requests will be issued: one request to remove entries for the previous FQDN and a second request to add entries for the new FQDN. In the last case, a lease release, a single DDNS request to remove its entries will be made. The decision making involved when granting a new lease is more involved and is discussed next. b10-dhcp6 will generate a DDNS update request only if the DHCP REQUEST contains the FQDN option (code 39). By default b10-dhcp6 will respect the FQDN N and S flags specified by the client as shown in the following table: Client Flags:N-S Client Intent Server Response Server Flags:N-S-O 0-0 Client wants to do forward updates, server should do reverse updates Server generates reverse-only request 1-0-0 0-1 Server should do both forward and reverse updates Server generates request to update both directions 0-1-0 1-0 Client wants no updates done Server does not generate a request 1-0-0 The first row in the table above represents "client delegation". Here the DHCP client states that it intends to do the forward DNS updates and the server should do the reverse updates. By default, b10-dhcp6 will honor the client's wishes and generate a DDNS request to D2 to update only reverse DNS data. The parameter, "override-client-update", can be used to instruct the server to override client delegation requests. When this parameter is true, b10-dhcp6 will disregard requests for client delegation and generate a DDNS request to update both forward and reverse DNS data. In this case, the N-S-O flags in the server's response to the client will be 0-1-1 respectively. (Note that the flag combination N=1, S=1 is prohibited according to RFC 4702. If such a combination is received from the client, the packet will be dropped by b10-dhcp6.) To override client delegation, issue the following commands: > config set Dhcp6/dhcp-ddns/override-client-update true > config commit The third row in the table above describes the case in which the client requests that no DNS updates be done. The parameter, "override-no-update", can be used to instruct the server to disregard the client's wishes. When this parameter is true, b10-dhcp6 will generate DDNS update request to D2 even if the client requests no updates be done. The N-S-O flags in the server's response to the client will be 0-1-1. To override client delegation, issue the following commands: > config set Dhcp6/dhcp-ddns/override-no-update true > config commit

Each NameChangeRequest must of course include the fully qualified domain name whose DNS entries are to be affected. b10-dhcp6 can be configured to supply a portion or all of that name based upon what it receives from the client in the DHCP REQUEST. The rules for determining the FQDN option are as follows: If configured to do so ignore the REQUEST contents and generate a FQDN using a configurable prefix and suffix. Otherwise, using is the domain name value from the client FQDN option as the candidate name: If the candidate name is a fully qualified domain name then use it. If the candidate name is a partial (i.e. unqualified) name then add a configurable suffix to the name and use the result as the FQDN. If the candidate name is a empty then generate a FQDN using a configurable prefix and suffix. To instruct b10-dhcp6 to always generate a FQDN, set the parameter "replace-client-name" to true: > config set Dhcp6/dhcp-ddns/replace-client-name true > config commit The prefix used when generating a FQDN is specified by the "generated-prefix" parameter. The default value is "myhost". To alter its value, simply set it to the desired string: > config set Dhcp6/dhcp-ddns/generated-prefix "another.host" > config commit The suffix used when generating a FQDN or when qualifying a partial name is specified by the "qualifying-suffix" parameter. The default value is "example.com". To alter its value simply set it to the desired string: > config set Dhcp6/dhcp-ddns/generated-prefix "our.net" > config commit

When qualifying a partial name, b10-dhcp6 will construct a name with the format: [candidate-name].[qualifying-suffix]. where candidate-name is the partial name supplied in the REQUEST. For example, if FQDN domain name value was "some-computer" and assuming the default value for qualifying-suffix, the generated FQDN would be: some-computer.example.com. When generating a the entire name, b10-dhcp6 will construct name of the format: [generated-prefix]-[address-text].[qualifying-suffix]. where address-text is simply the lease IP address converted to a hyphenated string. For example, if lease address is 3001:1::70E and assuming default values for generated-prefix and qualifying-suffix, the generated FQDN would be: myhost-3001-1--70E.example.com.

The DHCPv6 protocol uses a "server identifier" (also known as a DUID) for clients to be able to discriminate between several servers present on the same link. There are several types of DUIDs defined, but RFC 3315 instructs servers to use DUID-LLT if possible. This format consists of a link-layer (MAC) address and a timestamp. When started for the first time, the DHCPv6 server will automatically generate such a DUID and store the chosen value to a file. That file is read by the server and the contained value used whenever the server is subsequently started. It is unlikely that this parameter should ever need to be changed. However, if such a need arises, stop the server, edit the file and restart the server. (The file is named b10-dhcp6-serverid and by default is stored in the "var" subdirectory of the directory in which BIND 10 is installed. This can be changed when BIND 10 is built by using "--localstatedir" on the "configure" command line.) The file is a text file that contains double digit hexadecimal values separated by colons. This format is similar to typical MAC address format. Spaces are ignored. No extra characters are allowed in this file.

The relay has to have an interface connected to the link on which the clients are being configured. Typically the relay has a global IPv6 address configured on that interface that belongs to the subnet that the server will assign addresses from. In such typical case, the server is able to use IPv6 address inserted by the relay (in link-addr field in RELAY-FORW message) to select appropriate subnet. However, that is not always the case. The relay address may not match the subnet in certain deployments. This usually means that there is more than one subnet allocated for a given link. Two most common examples where this is the case are long lasting network renumbering (where both old and new address space is still being used) and a cable network. In a cable network both cable modems and the devices behind them are physically connected to the same link, yet they use distinct addressing. In such case, the DHCPv6 server needs additional information (like the value of interface-id option or IPv6 address inserted in the link-addr field in RELAY-FORW message) to properly select an appropriate subnet. The following example assumes that there is a subnet 2001:db8:1::/64 that is accessible via relay that uses 3000::1 as its IPv6 address. The server will be able to select this subnet for any incoming packets that came from a relay that has an address in 2001:db8:1::/64 subnet. It will also select that subnet for a relay with address 3000::1. > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "2001:db8:1::/64" > config set Dhcp6/subnet6[0]/pool [ "2001:db8:1::2 - 2001:db8:1::ffff" ] > config set Dhcp6/subnet6[0]/relay/ip-address "3000::1" > config commit

In certain cases, it is useful to mix relay address information, introduced in with client classification, explained in . One specific example is cable network, where typically modems get addresses from a different subnet than all devices connected behind them. Let's assume that there is one CMTS (Cable Modem Termination System) with one CM MAC (a physical link that modems are connected to). We want the modems to get addresses from the 3000::/64 subnet, while everything connected behind modems should get addresses from another subnet (2001:db8:1::/64). The CMTS that acts as a relay an uses address 3000::1. The following configuration can serve that configuration: > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[0]/subnet "3000::/64" > config set Dhcp6/subnet6[0]/pool [ "3000::2 - 3000::ffff" ] > config set Dhcp6/subnet6[0]/client-class "docsis3.0" > config set Dhcp6/subnet6[0]/relay/ip-address "3000::1" > config add Dhcp6/subnet6 > config set Dhcp6/subnet6[1]/subnet "2001:db8:1::/64" > config set Dhcp6/subnet6[1]/pool [ "2001:db8:1::1 - 2001:db8:1::ffff" ] > config set Dhcp6/subnet6[1]/relay/ip-address "3000::1" > config commit

The following standards and draft standards are currently supported: RFC 3315: Supported messages are SOLICIT, ADVERTISE, REQUEST, RELEASE, RENEW, REBIND and REPLY. RFC 3633: Supported options are IA_PD and IA_PREFIX. Also supported is the status code NoPrefixAvail. RFC 3646: Supported option is DNS_SERVERS. RFC 4704: Supported option is CLIENT_FQDN.

These are the current limitations and known problems with the DHCPv6 server software. Most of them are reflections of the early stage of development and should be treated as not implemented yet, rather than actual limitations. On-line configuration has some limitations. Adding new subnets or modifying existing ones work, as is removing the last subnet from the list. However, removing non-last (e.g. removing subnet 1,2 or 3 if there are 4 subnets configured) will cause issues. The problem is caused by simplistic subnet-id assignment. The subnets are always numbered, starting from 1. That subnet-id is then used in leases that are stored in the lease database. Removing non-last subnet will cause the configuration information to mismatch data in the lease database. It is possible to manually update subnet-id fields in MySQL or PostgreSQL database, but it is awkward and error prone process. A better reconfiguration support is planned. On startup, the DHCPv6 server does not get the full configuration from BIND 10. To remedy this, after starting BIND 10, modify any parameter and commit the changes, e.g. > config show Dhcp6/renew-timer Dhcp6/renew-timer 1000 integer (default) > config set Dhcp6/renew-timer 1001 > config commit Temporary addresses are not supported. The server will allocate, renew or rebind a maximum of one lease for a particular IA option (IA_NA or IA_PD) sent by a client. RFC 3315 and RFC 3633 allow for multiple addresses or prefixes to be allocated for a single IA. Temporary addresses are not supported. Confirmation (CONFIRM), duplication report (DECLINE), stateless configuration (INFORMATION-REQUEST) and client reconfiguration (RECONFIGURE) are not yet supported. The server doesn't act upon expired leases. In particular, when a lease expires, the server doesn't request removal of the DNS records associated with it.

The DHCP-DDNS Server (b10-dhcp-ddns, known informally as D2) conducts the client side of the DDNS protocol (defined in RFC 2136) on behalf of the DHCPv4 and DHCPv6 servers (b10-dhcp4 and b10-dhcp6 respectively). The DHCP servers construct DDNS update requests, known as NameChangeRequests (NCRs), based upon DHCP lease change events and then post these to D2. D2 attempts to match each such request to the appropriate DNS server(s) and carry out the necessary conversation with those servers to update the DNS data. In order to match a request to appropriate DNS servers, D2 must have a catalog of servers from which to select. In fact, D2 has two such catalogs, one for forward DNS and one for reverse DNS; these catalogs are referred to as DDNS Domain Lists. Each list consists of one or more named DDNS Domains. Further, each DDNS Domain has a list of of one or more DNS servers that publish the DNS data for that domain. When conducting forward domain matching, D2 will compare the FQDN in the request against the name of each forward DDNS Domain. The domain whose name matches the longest portion of the FQDN is considered the best match. For example, if the FQDN is "myhost.sample.example.com.", and there are two forward domains in the catalog: "sample.example.com." and "example.com.", the former is regarded as the best match. In some cases, it may not be possible to find a suitable match. Given the same two forward domains there would be no match for the FQDN, "bogus.net", so the request would be rejected. Finally, if there are no forward DDNS Domains defined, D2 will simply disregard the forward update portion of requests. When conducting reverse domain matching, D2 constructs a reverse FQDN from the lease address in the request and compare that against the name of each reverse DDNS Domain. Again, the domain whose name matches the longest portion of the FQDN is considered the best match. For instance, if the lease address is "172.16.1.40" and there are two reverse domains in the catalog: "1.16.172.in-addr.arpa." and "16.172.in-addr.arpa", the former is the best match. As with forward matching, it is possible to not find a suitable match. Given the same two domains, there would be no match for the lease address, "192.168.1.50", and the request would be rejected. Finally, if there are no reverse DDNS Domains defined, D2 will simply disregard the reverse update portion of requests.

b10-dhcp-ddns is the BIND 10 DHCP-DDNS server and, like other parts of BIND 10, is configured through the bindctl program. After starting BIND 10 and entering bindctl, the first step in configuring the server is to add it to the list of running BIND 10 services. > config add Init/components b10-dhcp-ddns > config set Init/components/b10-dhcp-ddns/kind dispensable > config commit To remove b10-dhcp-ddns from the set of running services, the b10-dhcp-ddns is removed from list of Init components: > config remove Init/components b10-dhcp-ddns > config commit Note that the server was only removed from the list, so it will not be automatically restarted, but the server itself is still running. Hence it is usually desired to stop it: > DhcpDdns shutdown Upon start up the module will load its configuration and begin listening for NCRs based on that configuration.

Once the server is started, it can be configured. To view the current configuration, use the following command in bindctl: > config show DhcpDdns When starting b10-dhcp-ddns module for the first time, the default configuration will be available. It will look similar to this: > config show DhcpDdns DhcpDdns/ip_address "127.0.0.1" string (default) DhcpDdns/port 53001 integer (default) DhcpDdns/dns_server_timeout 100 integer (default) DhcpDdns/ncr_protocol "UDP" string (default) DhcpDdns/ncr_format "JSON" string (default) DhcpDdns/tsig_keys [] list (default) DhcpDdns/forward_ddns/ddns_domains [] list (default) DhcpDdns/reverse_ddns/ddns_domains [] list (default) (While displayed, the parameter "interface" is not implemented, and will be removed in the near future.) The configuration can be divided as follows, each of which is described in its own section: Global Server Parameters — values which control connectivity and global server behavior TSIG Key Info — defines the TSIG keys used for secure traffic with DNS servers Forward DDNS — defines the catalog of Forward DDNS Domains Reverse DDNS — defines the catalog of Forward DDNS Domains

ip_address - IP address on which D2 listens for requests. The default is the local loopback interface at address 127.0.0.1. You may specify either an IPv4 or IPv6 address. port - Port on which D2 listens for requests. The default value is 53001. ncr_format - Socket protocol to use when sending requests to D2. Currently only UDP is supported. TCP may be available in an upcoming release. ncr_protocol - Packet format to use when sending requests to D2. Currently only JSON format is supported. Other formats may be available in future releases. dns_server_timeout - The maximum amount of time in milliseconds, that D2 will wait for a response from a DNS server to a single DNS update message. D2 must listen for change requests on a known address and port. By default it listens at 127.0.0.1 on port 53001. The following example illustrates how to change D2's global parameters so it will listen at 192.168.1.10 port 900: > config set DhcpDdns/ip_address "192.168.1.10" > config set DhcpDdns/port 900 > config commit When the DHCP-DDNS server is configured to listen at an address other than the loopback address (127.0.0.1 or ::1), it is possible for a malicious attacker to send bogus NameChangeRequests to it and change entries in the DNS. For this reason, addresses other than the IPv4 or IPv6 loopback addresses should only be used for testing purposes. A future version of Kea will implement authentication to guard against such attacks. If the ip_address and port are changed, it will be necessary to change the corresponding values in the DHCP servers' "dhcp-ddns" configuration section.

A DDNS protocol exchange can be conducted with or without TSIG (defined in RFC 2845). This configuration section allows the administrator to define the set of TSIG keys that may be used in such exchanges. To use TSIG when updating entries in a DNS Domain, a key must be defined in the TSIG Key List and referenced by name in that domain's configuration entry. When D2 matches a change request to a domain, it checks whether the domain has a TSIG key associated with it. If so, D2 will use that key to sign DNS update messages sent to and verify repsonses received from the domain's DNS server(s). For each TSIG key required by the DNS servers that D2 will be working with there must be a corresponding TSIG key in the TSIG Key list. As one might gather from the name, the tsig_key section of the D2 configuration lists the TSIG keys. Each entry describes a TSIG key used by one or more DNS servers to authenticate requests and sign responses. Every entry in the list has three parameters: name — a unique text label used to identify this key within the list. This value is used to specify which key (if any) should be used when updating a specific domain. So long as it is unique its content is arbitrary, although for clarity and ease of maintenance it is recommended that it match the name used on the DNS server(s). It cannot be blank. algorithm — specifies which hashing algorithm should be used with this key. This value must specify the same algorithm used for the key on the DNS server(s). The supported algorithms are listed below: HMAC-MD5 HMAC-SHA1 HMAC-SHA224 HMAC-SHA256 HMAC-SHA384 HMAC-SHA512 This value is not case sensitive. secret — is used to specify the shared secret key code for this key. This value is case sensitive and must exactly match the value specified on the DNS server(s). It is a base64-encoded text value. As an example, suppose that a domain D2 will be updating is maintained by a BIND9 DNS server which requires dynamic updates to be secured with TSIG. Suppose further that the entry for the TSIG key in BIND9's named.conf file looks like this: : key "key.four.example.com." { algorithm hmac-sha224; secret "bZEG7Ow8OgAUPfLWV3aAUQ=="; }; : By default, the TSIG Key list is empty: > config show DhcpDdns/tsig_keys DhcpDdns/tsig_keys [] list (default) We must first create a new key in the list: > config add DhcpDdns/tsig_keys Displaying the new element, reveals: > config show DhcpDdns/tsig_keys[0] DhcpDdns/tsig_keys[0]/name "" string (default) DhcpDdns/tsig_keys[0]/algorithm "HMAC-MD5" string (modified) DhcpDdns/tsig_keys[0]/secret "" string (default) Now set all three values to match BIND9's key: > config set DhcpDdns/tsig_keys[0]/name "key.four.example.com" > config set DhcpDdns/tsig_keys[0]/algorithm "HMAC-SHA224" > config set DhcpDdns/tsig_keys[0]/secret "bZEG7Ow8OgAUPfLWV3aAUQ==" > config commit These steps would be repeated for each TSIG key needed. Note that the same TSIG key can be used with more than one domain.

The Forward DDNS section is used to configure D2's forward update behavior. Currently it contains a single parameter, the catalog of forward DDNS Domains: > config show DhcpDdns/forward_ddns/ DhcpDdns/forward_ddns/ddns_domains [] list (default) By default, this list is empty, which will cause the server to ignore the forward update portions of requests.

A forward DDNS Domain maps a forward DNS zone to a set of DNS servers which maintain the forward DNS data for that zone. You will need one forward DDNS Domain for each zone you wish to service. It may very well be that some or all of your zones are maintained by the same servers. You will still need one DDNS Domain per zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS Domain only defines a single zone. The section describes how to add Forward DDNS Domains. Repeat these steps for each Forward DDNS Domain desired. Each Forward DDNS Domain has the following parameters: name — The fully qualified domain name (or zone) that this DDNS Domain can update. This is value used to compare against the request FQDN during forward matching. It must be unique within the catalog. key_name — If TSIG is used with this domain's servers, this value should be the name of the key from within the TSIG Key List to use. If the value is blank (the default), TSIG will not be used in DDNS conversations with this domain's servers. Currently TSIG has not been implemented, so this value is ignored. dns_servers — A list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. The servers are used in a first to last preference. In other words, when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it. If that attempt fails, it will move to next one in the list and so on until the it achieves success or the list is exhausted. To create a new forward DDNS Domain, one must first add a new domain element: > config add DhcpDdns/forward_ddns/ddns_domains Displaying the DDNS Domain reveals this: > config show DhcpDdns/forward_ddns/ddns_domains[0] DhcpDdns/forward_ddns/ddns_domains[0]/name "" string (default) DhcpDdns/forward_ddns/ddns_domains[0]/key_name "" string (default) DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers [] list (default) To set the domain's name to "other.example.com": > config set DhcpDdns/forward_ddns/ddns_domains[1]/name "other.example.com" > config commit It is permissible to add a domain without any servers. If that domain should be matched to a request, however, the request will fail. In order to make the domain useful though, we must add at least one DNS server to it.

The section describes how to add DNS servers to a Forward DDNS Domain. Repeat them for as many servers as desired for a each domain. Forward DNS Server entries represent actual DNS servers which support the server side of the DDNS protocol. Each Forward DNS Server has the following parameters: hostname — The resolvable host name of the DNS server. This value is not yet implemented. ip_address — The IP address at which the server listens for DDNS requests. This may be either an IPv4 or an IPv6 address. port — The port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53. To create a new forward DNS Server, one must first add a new server element to the domain: > config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers Displaying the DNS Server element should appear as follows: > config show DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0] DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/hostname "" string (default) DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address "" string (default) DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/port 53 integer(default) As stated earlier, "hostname" is not yet supported so, the parameter "ip_address" must be set to the address of the DNS server. If for example the service is running at "172.88.99.10", then set it as follows: > config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.88.99.10" > config commit

The Reverse DDNS section is used to configure D2's reverse update behavior, and the concepts are the same as for the forward DDNS section. Currently it contains a single parameter, the catalog of reverse DDNS Domains: > config show DhcpDdns/reverse_ddns/ DhcpDdns/reverse_ddns/ddns_domains [] list (default) By default, this list is empty, which will cause the server to ignore the reverse update portions of requests.

A reverse DDNS Domain maps a reverse DNS zone to a set of DNS servers which maintain the reverse DNS data for that zone. You will need one reverse DDNS Domain for each zone you wish to service. It may very well be that some or all of your zones are maintained by the same servers; even then, you will still need one DDNS Domain entry for each zone. Remember that matching a request to the appropriate server(s) is done by zone and a DDNS Domain only defines a single zone. The section describes how to add Reverse DDNS Domains. Repeat these steps for each Reverse DDNS Domain desired. Each Reverse DDNS Domain has the following parameters: name — The fully qualified reverse zone that this DDNS Domain can update. This is the value used during reverse matching which will compare it with a reversed version of the request's lease address. The zone name should follow the appropriate standards: for example, to to support the IPv4 subnet 172.16.1, the name should be. "1.16.172.in-addr.arpa.". Similarly, to support an IPv6 subent of 2001:db8:1, the name should be "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa." Whatever the name, it must be unique within the catalog. key_name — If TSIG should be used with this domain's servers, then this value should be the name of that key from the TSIG Key List. If the value is blank (the default), TSIG will not be used in DDNS conversations with this domain's servers. Currently this value is not used as TSIG has not been implemented. dns_servers — a list of one or more DNS servers which can conduct the server side of the DDNS protocol for this domain. Currently the servers are used in a first to last preference. In other words, when D2 begins to process a request for this domain it will pick the first server in this list and attempt to communicate with it. If that attempt fails, it will move to next one in the list and so on until the it achieves success or the list is exhausted. To create a new reverse DDNS Domain, one must first add a new domain element: > config add DhcpDdns/reverse_ddns/ddns_domains Displaying the DDNS Domain reveals this: > config show DhcpDdns/reverse_ddns/ddns_domains[0] DhcpDdns/reverse_ddns/ddns_domains[0]/name "" string (default) DhcpDdns/reverse_ddns/ddns_domains[0]/key_name "" string (default) DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers [] list (default) For domain supporting the subnet 2001:db8:1::, we would set the domain's name as follows: > config set DhcpDdns/reverse_ddns/ddns_domains[1]/name "1.0.0.0.8.B.D.0.1.0.0.2.ip6.arpa." > config commit It is permissible to add a domain without any servers. If that domain should be matched to a request, however, the request will fail. In order to make the domain useful though, we must add at least one DNS server to it.

The section describes how to add DNS servers to a Reverse DDNS Domain. Repeat them for as many servers as desired for a each domain. Reverse DNS Server entries represents a actual DNS servers which support the server side of the DDNS protocol. Each Reverse DNS Server has the following parameters: hostname — The resolvable host name of the DNS server. This value is currently ignored. ip_address — The IP address at which the server listens for DDNS requests. port — The port on which the server listens for DDNS requests. It defaults to the standard DNS service port of 53. To create a new reverse DNS Server, one must first add a new server element to the domain: > config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers Displaying the DNS Server element should appear as follows: > config show DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0] DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/hostname "" string (default) DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address "" string (default) DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/port 53 integer(default) As stated earlier, "hostname" is not yet supported so, the parameter "ip_address" must be set to the address of the DNS server. If for example the service is running at "172.88.99.10", then set it as follows: > config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.88.99.10" > config commit

This section provides an example DHCP-DDNS server configuration based on a small example network. Let's suppose our example network has three domains, each with their own subnet. Domain Subnet Forward DNS Servers Reverse DNS Servers four.example.com 192.0.2.0/24 172.16.1.5, 172.16.2.5 172.16.1.5, 172.16.2.5 six.example.com 2001:db8:1::/64 3001:1::50 3001:1::51 example.com 192.0.0.0/16 172.16.2.5 172.16.2.5 We need to construct three forward DDNS Domains: # DDNS Domain Name DNS Servers 1. four.example.com. 172.16.1.5, 172.16.2.5 2. six.example.com. 3001:1::50 3. example.com. 172.16.2.5 As discussed earlier, FQDN to domain matching is based on the longest match. The FQDN, "myhost.four.example.com.", will match the first domain ("four.example.com") while "admin.example.com." will match the third domain ("example.com"). The FQDN, "other.example.net." will fail to match any domain and would be rejected. The following series of commands in bindctl will create the Forward DDNS Domains. > config add DhcpDdns/forward_ddns/ddns_domains > config set DhcpDdns/forward_ddns/ddns_domains[0]/name "four.example.com." > config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers > config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.16.1.5" > config add DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers > config set DhcpDdns/forward_ddns/ddns_domains[0]/dns_servers[1]/ip_address "172.16.2.5" > > config add DhcpDdns/forward_ddns/ddns_domains > config set DhcpDdns/forward_ddns/ddns_domains[1]/name "six.example.com." > config add DhcpDdns/forward_ddns/ddns_domains[1]/dns_servers > config set DhcpDdns/forward_ddns/ddns_domains[1]/dns_servers[0]/ip_address "3001:1::50:" > > config add DhcpDdns/forward_ddns/ddns_domains > config set DhcpDdns/forward_ddns/ddns_domains[2]/name "example.com." > config add DhcpDdns/forward_ddns/ddns_domains[2]/dns_servers > config set DhcpDdns/forward_ddns/ddns_domains[2]/dns_servers[0]/ip_address "172.16.2.5" > > config commit Similarly, we need to construct the three reverse DDNS Domains: # DDNS Domain Name DNS Servers 1. 2.0.192.in-addr.arpa. 172.16.1.5, 172.16.2.5 2. 1.0.0.0.8.d.b.0.1.0.0.2.ip6.arpa. 3001:1::50 3. 0.182.in-addr.arpa. 172.16.2.5 An address of "192.0.2.150" will match the first domain, "2001:db8:1::10" will match the second domain, and "192.0.50.77" the third domain. The following series of commands in bindctl will create our Reverse DDNS Domains. > config add DhcpDdns/reverse_ddns/ddns_domains > config set DhcpDdns/reverse_ddns/ddns_domains[0]/name "2.0.192.in-addr.arpa." > config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers > config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[0]/ip_address "172.16.1.5" > config add DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers > config set DhcpDdns/reverse_ddns/ddns_domains[0]/dns_servers[1]/ip_address "172.16.2.5" > > config add DhcpDdns/reverse_ddns/ddns_domains > config set DhcpDdns/reverse_ddns/ddns_domains[1]/name "1.0.0.0.8.d.b.0.1.0.0.2.ip6.arpa." > config add DhcpDdns/reverse_ddns/ddns_domains[1]/dns_servers > config set DhcpDdns/reverse_ddns/ddns_domains[1]/dns_servers[0]/ip_address "3001:1::50:" > > config add DhcpDdns/reverse_ddns/ddns_domains > config set DhcpDdns/reverse_ddns/ddns_domains[2]/name "0.192.in-addr.arpa." > config add DhcpDdns/reverse_ddns/ddns_domains[2]/dns_servers > config set DhcpDdns/reverse_ddns/ddns_domains[2]/dns_servers[0]/ip_address "172.16.2.5" > > config commit

The following are the current limitations of the DHCP-DDNS Server. Requests received from the DHCP servers are placed in a queue until they are processed. Currently all queued requests are lost when the server shuts down. TSIG Authentication (RFC 2845) is not supported yet.

libdhcp++ is a common library written in C++ that handles many DHCP-related tasks, including: DHCPv4 and DHCPv6 packets parsing, manipulation and assembly Option parsing, manipulation and assembly Network interface detection Socket operations such as creation, data transmission and reception and socket closing. While this library is currently used by Kea, it is designed to be a portable, universal library, useful for any kind of DHCP-related software.

Both the DHCPv4 and DHCPv6 components share network interface detection routines. Interface detection is currently supported on Linux, all BSD family (FreeBSD, NetBSD, OpenBSD), Mac OS X and Solaris 11 systems. DHCPv4 requires special raw socket processing to send and receive packets from hosts that do not have IPv4 address assigned yet. Support for this operation is implemented on Linux only, so it is likely that DHCPv4 component will not work in certain cases on systems other than Linux.

The b10-stats process is started by b10-init. It periodically collects statistics data from various modules and aggregates it. This stats daemon provides commands to identify if it is running, show specified or all statistics data, and show specified or all statistics data schema. For example, using bindctl: > Stats show { "Auth": { "opcode.iquery": 0, "opcode.notify": 10, "opcode.query": 869617, ... "queries.tcp": 1749, "queries.udp": 867868 }, "Init": { "boot_time": "2011-01-20T16:59:03Z" }, "Stats": { "boot_time": "2011-01-20T16:59:05Z", "last_update_time": "2011-01-20T17:04:05Z", "lname": "4d3869d9_a@jreed.example.net", "report_time": "2011-01-20T17:04:06Z", "timestamp": 1295543046.823504 } }

The logging system in Kea is configured through the Logging module. All modules will look at the configuration in Logging to see what should be logged and to where.

Within Kea, a message is logged through a component called a "logger". Different parts of log messages through different loggers, and each logger can be configured independently of one another. In the Logging module, you can specify the configuration for zero or more loggers; any that are not specified will take appropriate default values. The three most important elements of a logger configuration are the name (the component that is generating the messages), the severity (what to log), and the output_options (where to log).

Each logger in the system has a name, the name being that of the component using it to log messages. For instance, if you want to configure logging for the Dhcp4 module, you add an entry for a logger named Dhcp4. This configuration will then be used by the loggers in the Dhcp4 module, and all the libraries used by it. If you want to specify logging for one specific library within the module, you set the name to module.library. For example, the logger used by the nameserver address store component has the full name of Dhcp4.dhcpsrv. If there is no entry in Logging for a particular library, it will use the configuration given for the module. To illustrate this, suppose you want the dhcpsrv library to log messages of severity DEBUG, and the rest of the Dhcp4 code to log messages of severity INFO. To achieve this you specify two loggers, one with the name Dhcp4 and severity INFO, and one with the name Dhcp4.dhcpsrv with severity DEBUG. As there are no entries for other libraries, they will use the configuration for the module (Dhcp4), so giving the desired behavior. One special case is that of a module name of * (asterisks), which is interpreted as any module. You can set global logging options by using this, including setting the logging configuration for a library that is used by multiple modules (e.g. *.config specifies the configuration library code in whatever module is using it). If there are multiple logger specifications in the configuration that might match a particular logger, the specification with the more specific logger name takes precedence. For example, if there are entries for both * and Dhcp4, the Dhcp4 module — and all libraries it uses — will log messages according to the configuration in the second entry (Dhcp4). All other modules will use the configuration of the first entry (*). One final note about the naming. When specifying the module name within a logger, use the name of the module as specified in bindctl, e.g. Dhcp4 for the Dhcp4 module, Dhcp6 for the Dhcp6 module, etc. When the message is logged, the message will include the name of the logger generating the message, but with the module name replaced by the name of the process implementing the module (so for example, a message generated by the Dhcp4 logger will appear in the output with a logger name of b10-dhcp4).

This specifies the category of messages logged. Each message is logged with an associated severity which may be one of the following (in descending order of severity): FATAL ERROR WARN INFO DEBUG When the severity of a logger is set to one of these values, it will only log messages of that severity, and the severities above it. The severity may also be set to NONE, in which case all messages from that logger are inhibited.

Each logger can have zero or more output_options. These specify where log messages are sent to. These are explained in detail below. The other options for a logger are:

When a logger's severity is set to DEBUG, this value specifies what debug messages should be printed. It ranges from 0 (least verbose) to 99 (most verbose). If severity for the logger is not DEBUG, this value is ignored.

If this is true, the output_options from the parent will be used. For example, if there are two loggers configured; Dhcp4 and Dhcp4.dhcpsrv, and additive is true in the second, it will write the log messages not only to the destinations specified for Dhcp4.dhcpsrv, but also to the destinations as specified in the output_options in the logger named Dhcp4.

The main settings for an output option are the destination and a value called output, the meaning of which depends on the destination that is set.

The destination is the type of output. It can be one of: console file syslog

Depending on what is set as the output destination, this value is interpreted as follows: destination is console The value of output must be one of stdout (messages printed to standard output) or stderr (messages printed to standard error). Note: if output is set to stderr and a lot of messages are produced in a short time (e.g. if the logging level is set to DEBUG), you may occasionally see some messages jumbled up together. This is due to a combination of the way that messages are written to the screen and the unbuffered nature of the standard error stream. If this occurs, it is recommended that output be set to stdout. destination is file The value of output is interpreted as a file name; log messages will be appended to this file. destination is syslog The value of output is interpreted as the syslog facility (e.g. local0) that should be used for log messages. The other options for output_options are:

Flush buffers after each log message. Doing this will reduce performance but will ensure that if the program terminates abnormally, all messages up to the point of termination are output.

Only relevant when destination is file, this is maximum file size of output files in bytes. When the maximum size is reached, the file is renamed and a new file opened. (For example, a ".1" is appended to the name — if a ".1" file exists, it is renamed ".2", etc.) If this is 0, no maximum file size is used. Due to a limitation of the underlying logging library (log4cplus), rolling over the log files (from ".1" to ".2", etc) may show odd results: There can be multiple small files at the timing of roll over. This can happen when multiple processes try to roll over the files simultaneously. Version 1.1.0 of log4cplus solved this problem, so if this or higher version of log4cplus is used to build Kea, it shouldn't happen. Even for older versions it is normally expected to happen rarely unless the log messages are produced very frequently by multiple different processes.

Maximum number of old log files to keep around when rolling the output file. Only relevant when destination is file.

In this example we want to set the global logging to write to the file /var/log/my_bind10.log, at severity WARN. We want the authoritative server to log at DEBUG with debuglevel 40, to a different file (/tmp/debug_messages). Start bindctl. ["login success "] > config show Logging Logging/loggers [] list By default, no specific loggers are configured, in which case the severity defaults to INFO and the output is written to stderr. Let's first add a default logger: > config add Logging/loggers > config show Logging Logging/loggers/ list (modified) The loggers value line changed to indicate that it is no longer an empty list: > config show Logging/loggers Logging/loggers[0]/name "" string (default) Logging/loggers[0]/severity "INFO" string (default) Logging/loggers[0]/debuglevel 0 integer (default) Logging/loggers[0]/additive false boolean (default) Logging/loggers[0]/output_options [] list (default) The name is mandatory, so we must set it. We will also change the severity as well. Let's start with the global logger. > config set Logging/loggers[0]/name * > config set Logging/loggers[0]/severity WARN > config show Logging/loggers Logging/loggers[0]/name "*" string (modified) Logging/loggers[0]/severity "WARN" string (modified) Logging/loggers[0]/debuglevel 0 integer (default) Logging/loggers[0]/additive false boolean (default) Logging/loggers[0]/output_options [] list (default) Of course, we need to specify where we want the log messages to go, so we add an entry for an output option. > config add Logging/loggers[0]/output_options > config show Logging/loggers[0]/output_options Logging/loggers[0]/output_options[0]/destination "console" string (default) Logging/loggers[0]/output_options[0]/output "stdout" string (default) Logging/loggers[0]/output_options[0]/flush false boolean (default) Logging/loggers[0]/output_options[0]/maxsize 0 integer (default) Logging/loggers[0]/output_options[0]/maxver 0 integer (default) These aren't the values we are looking for. > config set Logging/loggers[0]/output_options[0]/destination file > config set Logging/loggers[0]/output_options[0]/output /var/log/kea.log > config set Logging/loggers[0]/output_options[0]/maxsize 204800 > config set Logging/loggers[0]/output_options[0]/maxver 8 Which would make the entire configuration for this logger look like: > config show all Logging/loggers Logging/loggers[0]/name "*" string (modified) Logging/loggers[0]/severity "WARN" string (modified) Logging/loggers[0]/debuglevel 0 integer (default) Logging/loggers[0]/additive false boolean (default) Logging/loggers[0]/output_options[0]/destination "file" string (modified) Logging/loggers[0]/output_options[0]/output "/var/log/kea.log" string (modified) Logging/loggers[0]/output_options[0]/flush false boolean (default) Logging/loggers[0]/output_options[0]/maxsize 204800 integer (modified) Logging/loggers[0]/output_options[0]/maxver 8 integer (modified) That looks OK, so let's commit it before we add the configuration for the authoritative server's logger. > config commit Now that we have set it, and checked each value along the way, adding a second entry is quite similar. > config add Logging/loggers > config set Logging/loggers[1]/name Dhcp4 > config set Logging/loggers[1]/severity DEBUG > config set Logging/loggers[1]/debuglevel 40 > config add Logging/loggers[1]/output_options > config set Logging/loggers[1]/output_options[0]/destination file > config set Logging/loggers[1]/output_options[0]/output /tmp/dhcp4_debug.log > config commit And that's it. Once we have found whatever it was we needed the debug messages for, we can simply remove the second logger to let the DHCP server use the same settings as the rest. > config remove Logging/loggers[1] > config commit And every module will now be using the values from the logger named *.

Each message written to the configured logging destinations comprises a number of components that identify the origin of the message and, if the message indicates a problem, information about the problem that may be useful in fixing it. Consider the message below logged to a file: 2014-04-11 12:58:01.005 INFO [b10-dhcp4.dhcpsrv/27456] DHCPSRV_MEMFILE_DB opening memory file lease database: type=memfile universe=4 Note: the layout of messages written to the system logging file (syslog) may be slightly different. This message has been split across two lines here for display reasons; in the logging file, it will appear on one line.) The log message comprises a number of components: 2014-04-11 12:58:01.005 The date and time at which the message was generated. INFO The severity of the message. [b10-dhcp4.dhcpsrv/27456] The source of the message. This comprises two components: the BIND 10 process generating the message (in this case, b10-dhcp4) and the module within the program from which the message originated (which is the name of the common library used by DHCP server implementations). DHCPSRV_MEMFILE_DB The message identification. Every message in Kea has a unique identification, which can be used as an index into the Kea Messages Manual () from which more information can be obtained. opening memory file lease database: type=memfile universe=4 A brief description. Within this text, information relating to the condition that caused the message to be logged will be included. In this example, the information is logged that the in-memory lease database backend will be used to store DHCP leases.

Kea was initially implemented as a collection of applications within the BIND 10 framework. Hence, Kea development would not be possible without the generous support of BIND 10 project sponsors. JPRS and CIRA are Patron Level sponsors. AFNIC, CNNIC, CZ.NIC, DENIC eG, Google, RIPE NCC, Registro.br, .nz Registry Services, and Technical Center of Internet are current sponsors. Afilias, IIS.SE, Nominet, and SIDN were founding sponsors of the project. Support for the development of the DHCPv4, DHCPv6 and DHCP-DDNS components is provided by Comcast.