Same MAC address on two VLANs & subnets

[Gerald Vogt]

On Fri, Feb 24, 2012 at 11:47 AM,  <sthaug at nethelp.no> wrote:
>> Doesn't anybody here know whether a single client-id can have two
>> active leases in two different subnets?
>
> Yes it can. The fact that client-id overrides hardware address means
> that you cannot have two clients with the *same* client-id in the same
> subnet. But in different subnets you certainly can.

Then why is the first lease released the moment the second lease is requested?

This is an extract of the debug output. Lease 10.10.10.5 is active at
the beginning on vlan 10. Then I try to get another IP address on vlan
20 and I see this:

-------------

trying next lease matching client id: 10.20.20.8
Found lease for client id: 10.20.20.8.
trying next lease matching hw addr: 10.20.20.8
Found lease for hardware address: 10.20.20.8.
Found lease for requested address: 10.20.20.8.
hardware lease and uid lease are identical.
uid lease and ip lease are identical.
choosing lease on requested address.
Returning lease: 10.20.20.8.
...
lease 10.20.20.8 moves from free to free
lease 10.20.20.8: next binding state free
...
DHCPDISCOVER from 00:26:b9:ee:40:59 via eth3
...
DHCPOFFER on 10.20.20.8 to 00:26:b9:ee:40:59 (test) via eth3
...
bool: check (default) returns false
exec: evaluate: succeeded
trying next lease matching client id: 10.10.10.5
wrong network segment: 10.10.10.5
lease 10.10.10.5 moves from active to released
lease 10.10.10.5: next binding state free
trying next lease matching client id: 10.20.20.8
Found lease for client id: 10.20.20.8.
trying next lease matching hw addr: 10.10.10.5
not active or not mine to allocate: 10.10.10.5
trying next lease matching hw addr: 10.20.20.8
Found lease for hardware address: 10.20.20.8.
Found lease for requested address: 10.20.20.8.
hardware lease and uid lease are identical.
uid lease and ip lease are identical.
choosing lease on requested address.
Returning lease: 10.20.20.8.

----------------

As you can see in the process of DHCPOFFER is tries to find matching
lease using the client id, finds the 10.10.10.5 lease, decides it's in
the wrong network segment (which is correct, as it's in a different
VLAN), and moves the 10.10.10.5 lease from active to released. And
that's what I read in the source code, too.

Do you have a similar setup where you can actually see two active
leases for a client-id in different subnets?

Thx, Gerald