[Kea-users] reservation for the same host in several subnets

[Kevin P. Fleming]

On Mon, Aug 26, 2024, at 05:46, Darren Ankney wrote:
> Hi Marek,
>
> You might be right.  I do not know.  I think yes, if you need to have
> separate reservations for the two different interfaces, then you'd
> have to specify separate subnets.  Is there any particular reason that
> the client cannot obtain the same IP regardless of the interface that
> is connected (surely you are not connecting both interfaces
> simultaneously)?

Yes, there is, and it's the IAID. I tried for weeks to make this work and could not.

If you have a reservation for an IPv6 address for a host and the host connects using one interface, the address will be leased to that host using the combination of its DUID and IAID. If it then connects using the other interface, its attempt to obtain the same address will fail because the IP is already leased to the previous IAID, so it will get a random address from the pool (if there is one).

The result of my previous effort (and others who tried the same thing) was the open feature request for reservations to not generate leases at all, so that hosts can get the same address even if a non-critical portion of the host's identity (IAID in this case) changes.