DHCP on VLAN

[Glenn Satchell]

>X-Original-To: dhcp-users at webster.isc.org
>X-Umn-Remote-Mta: [N] 71-215-234-206.mpls.qwest.net [71.215.234.206] #+TS+AU+HN
>Date: Sat, 24 Feb 2007 11:07:31 -0600
>From: Tim Peiffer <peiffer at umn.edu>
>To: dhcp-users at isc.org
>Subject: Re: DHCP on VLAN
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>
>This is really a question for either Ted or ISC.  When I was 
>experimenting, I created my 30 vlans and I ended up patching a few 
>things to make it work.  Since then, I have had a number of 'upgrades' 
>to change out to GigE hardare, and reimplement DHCPD to account for the 
>current code and the limit on VLAN's hasn't shown up since.  I remember 
>there was an error message shortly after startup that indicated that 
>there wasn't any room left on the stack for numbers of interfaces.
>
>I would think that one limiting part of any multi-homed environment is 
>the amount of non-unicast traffic that the server sees.  Every broadcast 
>packet creates an interrupt and has to be inspected.
>
>Ted or ISC - do you know of any current limits on the number of 
>interfaces used for dhcpd?
>
>Tim Peiffer
>Networking and Telecommunications Services
>University of Minnesota
>
>> Secondary question of my own ...
>>
>> I've just set up a Debian Etch box doing VLAN trunking to a switch 
>> (for a multi-tennant gateway). DHCP appears to work fine on all the 
>> virtual interfaces, are there any 'gotchas' I should be aware of ?
>>   
>
>

The problem was a very long time ago, and was caused by a buffer that
was too small to hold a long list of interfaces. Might be this fix
(taken from 3.0.5 RELNOTES)? I can't recall hearing of this problem for
a very long time.

                Changes since 3.0 Beta 2 Patchlevel 5

- Fix a bug in the recent enhancement to the interface discovery code
  to support arbitrary-length interface lists.

regards,
-glenn