Automatic VLAN Assignment (AVA) - Problem with option routers

Tarik Gasmi tarik.gasmi at
Thu May 15 08:07:15 UTC 2008

thanks for the answers so far,
i did some sniffering with ethereal:

the option routers is requested from the client in both cycles
(parameter request list in DHCP Discover/Request Packet)

in the first cycle the correct option routers is sent back in DHCP
Offer/Ack packets (, and also option 43 with the new Voip
VLAN (so the client knows the correct VLAN in the second cycle)

the client releases

in the second cycle in the DHCP Offer/Ack packets the wrong option
routers is sent back from the server (still although the
client asks with correct VLAN Tag and gets an IP in the
correct Voip VLAN/Subnet.

however, when setting option routers in the scope of the
host-declaration of the client (and not only of the subnet), the option
is sent back correctly (

So i think that the problem is server side, because the server does not
send back the correct router option in the one case but does in the
other ...

why do i have to put it in the host scope? is this correlated to the
mac-address of the client somehow?

best regards,

Simon Hobson schrieb:
> Glenn Satchell wrote:
>> Hmm, same switch port with two different subnets - that's a shared
>> network. Try putting a shared-network statement around the two subnets,
>> eg:
> No, it may be the same physical socket, but it's different VLANs - so no
> shared network. It's a common source of confusion !


 Tarik Gasmi
 Rechenzentrum Universität Freiburg
 Hermann-Herder-Str.10 / 79104 Freiburg

 Email: tarik.gasmi at
 Tel.:  +49 (0)761 203-4674

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