]> Kea is designed to allow different methods by which it can be configured, each method being implemented by a component known as a configuration backend. At present, only one such backend is available, that allowing configuration by means of a JSON file.

JSON is the default configuration backend. It assumes that the servers are started from the command line (either directly or using a script, e.g. keactrl). The JSON backend uses certain signals to influence Kea. The configuration file is specified upon startup using the -c parameter.

Configuration files for DHCPv4, DHCPv6 and DDNS modules are defined in an extended JSON format. Basic JSON is defined in RFC 4627. Kea components use an extended JSON with additional features allowed: in that they allow shell-style shell comments: any text after the hash (#) character is ignored. Dhcp6 allows # in any column, while Dhcp4 and Ddns require hash to be in the first column. C comments: any text after the double slashes (//) character is ignored. We're in a process of migrating the configuation parsers and currently only Dhcp6 supports this feature. Multiline comments: any text between /* and */ is ignored. This commenting can span multiple lines. We're in a process of migrating the configuation parsers and currently only Dhcp6 supports this feature. File inclusion: JSON files can include other JSON files. This can be done by using <?include "file.json"?>. We're in a process of migrating the configuation parsers and currently only Dhcp6 supports this feature. The configuration file consists of a single object (often colloquially called a map) started with a curly bracket. It comprises the "Dhcp4", "Dhcp6", "DhcpDdns" and/or "Logging" objects. It is possible to define additional elements, but they will be ignored. For example, it is possible to define Dhcp4, Dhcp6 and Logging elements in a single configuration file that can be used to start both the DHCPv4 and DHCPv6 components. When starting, the DHCPv4 component will use Dhcp4 object to configure itself and the Logging object to configure logging parameters; it will ignore the Dhcp6 object. A very simple configuration for both DHCPv4 and DHCPv6 could look like this: # The whole configuration starts here. { # DHCPv4 specific configuration starts here. "Dhcp4": { "interfaces-config": { "interfaces": [ "eth0" ], "dhcp-socket-type": "raw" }, "valid-lifetime": 4000, "renew-timer": 1000, "rebind-timer": 2000, "subnet4": [{ "pools": [ { "pool": "192.0.2.1-192.0.2.200" } ], "subnet": "192.0.2.0/24" }] }, # DHCPv4 specific configuration ends here. # DHCPv6 specific configuration starts here. "Dhcp6": { "interfaces-config": { "interfaces": [ "eth1" ] }, "preferred-lifetime": 3000, "valid-lifetime": 4000, "renew-timer": 1000, "rebind-timer": 2000, "subnet6": [{ "pools": [ { "pool": "2001:db8::/80" } ], "subnet": "2001:db8::/64" }] }, # DHCPv6 specific configuration ends here. # Logger parameters (that could be shared among several components) start here. # This section is used by both the DHCPv4 and DHCPv6 servers. "Logging": { "loggers": [{ "name": "*", "severity": "DEBUG" }] } # Logger parameters end here. # The whole configuration structure ends here. } More examples are available in the installed share/doc/kea/examples directory. To avoid repetition of mostly similar structures, examples in the rest of this guide will showcase only the subset of parameters appropriate for a given context. For example, when discussing the IPv6 subnets configuration in DHCPv6, only subnet6 parameters will be mentioned. It is implied that the remaining elements (the global map that holds Dhcp6, Logging and possibly DhcpDdns) are present, but they are omitted for clarity. Usually, locations where extra parameters may appear are denoted by an ellipsis.

It is sometimes convenient to refer to a specific element in the configuration hierarchy. Each hierarchy level is separated by a slash. If there is an array, a specific instance within that array is referenced by a number in square brackets (with numbering starting at zero). For example, in the above configuration the valid-lifetime in the Dhcp6 component can be referred to as Dhcp6/valid-lifetime and the pool in the first subnet defined in the DHCPv6 configuration as Dhcp6/subnet6[0]/pool.