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@@ -2689,30 +2689,32 @@ should include options from the isc option space:
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addresses that it is expected to hand out to the DHCPv6 clients.
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It is assumed that the server is authoritative and has complete
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jurisdiction over those addresses. However, due to various
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- reasons, like misconfiguration or faulty client implenetation
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- that retains its address beyond valid lifetime, there may be
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+ reasons, such as misconfiguration or a faulty client implenetation
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+ that retains its address beyond the valid lifetime, there may be
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devices connected that use those addresses without the server's
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- approval or knowledge. Such an unwelcome event can be detected
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+ approval or knowledge.</para>
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+
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+ <para>Such an unwelcome event can be detected
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by legitimate clients (using Duplicate Address Detection) and
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- reported to the DHCPv6 server using DECLINE message. The server
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- will sanity check it (if the client declining an address really
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- was supposed to use it), then will conduct clean up operation
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+ reported to the DHCPv6 server using a DECLINE message. The server
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+ will do a sanity check (if the client declining an address really
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+ was supposed to use it), then will a conduct clean up operation
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and confirm it by sending back a REPLY message. Any DNS entries
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related to that address will be removed, the fact will be logged
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and hooks will be triggered. After that is done, the address
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will be marked as declined (which indicates that it is used by
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an unknown entity and thus not available for assignment to
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- anyone) and probation time on it will be set. Unless otherwise
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+ anyone) and a probation time will be set on it. Unless otherwise
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configured, the probation period lasts 24 hours. After that
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period, the server will recover the lease, i.e. put it back into
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- available state. The address will be available for assignment
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+ the available state. The address will be available for assignment
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again. It should be noted that if the underlying issue of a
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misconfigured device is not resolved, the duplicate address
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scenario will repeat. On the other hand, it provides an
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opportunity to recover from such an event automatically, without
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any sysadmin intervention.</para>
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- <para>To configure decline probation period to a value different
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+ <para>To configure the decline probation period to a value different
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than the default, the following syntax can be used:
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<screen>
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"Dhcp6": {
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@@ -2725,20 +2727,20 @@ should include options from the isc option space:
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the server to recycle declined leases after an hour.</para>
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<para>There are several statistics and hook points associated with the
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- Decline handling procedure. lease6_decline hook is triggered after the
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- incoming Decline message was sanitized and the server is about to decline
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- the lease. declined-addresses statistic is increased after the hook
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+ Decline handling procedure. The lease6_decline hook is triggered after the
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+ incoming Decline message has been sanitized and the server is about to decline
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+ the lease. The declined-addresses statistic is increased after the hook
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returns (both global and subnet specific variants).</para>
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<para>Once the probation time elapses, the declined lease is recovered
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- using standard expired lease reclaimation procedure, with several
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+ using the standard expired lease reclaimation procedure, with several
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additional steps. In particular, both declined-addresses statistics
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- (global and subnet specific) are being decreased. At the same time,
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+ (global and subnet specific) are decreased. At the same time,
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reclaimed-declined-addresses statistics (again in two variants, global and
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subnet specific) are increased.</para>
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<para>Note about statistics: The server does not decrease
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- assigned-addresses statistics when Decline message is received and
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+ assigned-addresses statistics when a DECLINE message is received and
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processed successfully. While technically a declined address is no longer
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assigned, the primary usage of the assigned-addresses statistic is to
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monitor pool utilization. Most people would forget to include
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@@ -3011,10 +3013,10 @@ should include options from the isc option space:
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<entry>
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This statistic shows the number of IPv6 adresses that are
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currently declined. This statistic counts the number of leases
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- being currently unavailable. Once the lease is recovered, this
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- statistic will be decreased. Ideally, this statistic should not
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- have non-zero values. If this statistic has non-zero or increasing
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- values, a network administrator should investigate if there is
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+ currently unavailable. Once a lease is recovered, this
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+ statistic will be decreased. Ideally, this statistic should be
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+ zero. If this statistic is non-zero (or worse increasing),
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+ a network administrator should investigate if there is
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a misbehaving device in his network. This is a global statistic
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that covers all subnets.
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</entry>
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@@ -3026,10 +3028,10 @@ should include options from the isc option space:
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<entry>
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This statistic shows the number of IPv6 adresses that are
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currently declined in a given subnet. This statistic counts the
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- number of leases being currently unavailable. Once the lease is
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+ number of leases currently unavailable. Once a lease is
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recovered, this statistic will be decreased. Ideally, this
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- statistic should not have non-zero values. If this statistic has
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- non-zero or increasing values, a network administrator should
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+ statistic should be zero. If this statistic is
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+ non-zero (or worse increasing), a network administrator should
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investigate if there is a misbehaving device in his network. The
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<emphasis>id</emphasis> is the subnet-id of a given subnet. This
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statistic is exposed for each subnet separately.
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@@ -3041,10 +3043,10 @@ should include options from the isc option space:
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<entry>integer</entry>
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<entry>
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This statistic shows the number of IPv6 adresses that were
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- declined, but are now recovered. Contrary to the
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+ declined, but are now recovered. Unlike
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declined-addresses, this statistic never decreases. It can be used
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as a long term indicator of how many actual valid Declines were
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- conducted and recovered from. This is a global statistic that
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+ processed and recovered from. This is a global statistic that
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covers all subnets.
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</entry>
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</row>
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@@ -3054,10 +3056,10 @@ should include options from the isc option space:
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<entry>integer</entry>
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<entry>
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This statistic shows the number of IPv6 adresses that were
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- declined, but are now recovered. Contrary to the
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+ declined, but are now recovered. Unlike
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declined-addresses, this statistic never decreases. It can be used
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as a long term indicator of how many actual valid Declines were
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- conducted and eventually recovered from. The
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+ processed and recovered from. The
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<emphasis>id</emphasis> is the subnet-id of a given subnet. This
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statistic is exposed for each subnet separately.
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</entry>
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