[Kea-users] Subnet/pool selection

Francis Dupont fdupont at isc.org
Mon Jan 21 23:57:50 UTC 2019

In a shared network the subnet selection in fact select the shared network.

When a host is looked up all the subnets of the shared network are scanned
starting from the selected one if there are less subnets than allowed
identifier types.

Pools are a bit different: they are scanned starting by the last used so
the selected subnet matters only once.

There is the code a comment explaining this mechanism:

 // Need to check if the subnet belongs to a shared network. If so,
 // we might be able to find a better subnet for lease allocation,
 // for which it is more likely that there are some leases available.
 // If we stick to the selected subnet, we may end up walking over
 // the entire subnet (or more subnets) to discover that the pools
 // have been exhausted. Using a subnet from which a lease was
 // assigned most recently is an optimization which increases
 // the likelyhood of starting from the subnet which pools are not
 // exhausted.

Francis Dupont <fdupont at isc.org>

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