pfSense

The lease allocation and reclamation behavior in Kea is more aggressive than that in ISC DHCP. As a consequence, users are being surprised by unexpected IP address changes when users leases had been fairly stable under ISC DHCP.

At the moment the only option users have to influence this is to greatly increase the default lease time (and maximum in certain cases), but Kea has other options to fine-tune its behavior.

See the Kea docs at https://kea.readthedocs.io/en/kea-2.6.1/arm/lease-expiration.html#lease-reclamation

We could use some global GUI options to tweak the behavior using the options listed in https://kea.readthedocs.io/en/kea-2.6.1/arm/lease-expiration.html#lease-reclamation-configuration-parameters -- they appear to be global options, not per-subnet, but it's possible they might work both ways. We could use default values for those which are much more lenient than Kea's own defaults.

As a part of improving the lease allocation behavior, we could also use a global option to drop or ignore DHCP release packets from clients which also trigger Kea to reclaim a lease immediately:

• https://kb.isc.org/docs/using-the-kea-dhcp-drop-class
• https://lists.isc.org/pipermail/kea-users/2021-November/003239.html

Feel free to kick it ahead to the next release if there is not enough time or it ends up being much more complicated.