Same MAC address on two VLANs & subnets

[Gerald Vogt]

On Fri, Feb 24, 2012 at 1:34 PM, Zhe Yao <zheyao at cim.mcgill.ca> wrote:
> Did you create two different virtual interfaces, e.g., eth0:0 and
> eth0:1, to connect to different VLANs?

No. It's two separate interfaces eth1 and eth3.

Thx, Gerald

>
> 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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