Same MAC address on two VLANs & subnets

[Zhe Yao]

Did you create two different virtual interfaces, e.g., eth0:0 and
eth0:1, to connect to different VLANs?

Best,
Zhe Yao
--------------
Department of Electrical and Computer Engineering
McGill University
Montreal, QC, Canada
H3A 2A7

zhe.yao at mail.mcgill.ca



On Fri, Feb 24, 2012 at 7:11 AM, Gerald Vogt <vogt at spamcop.net> wrote:
> 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
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