DHCP and multiple vlans

[Guy Antony Halse]

I'm trying to configure a FreeBSD 5.1-RELEASE system to act as the default
gateway for several virtual lans.  I've got two NICs in the box, one which
supplies the uplink, and one which has about 40 vlan(4) vlans on it.

I was trying to run isc-dhcp3's dhcrelay to relay DHCP messages to our DHCP
server when I ran into a problem.  Only the first ten vlans (vlan0 through
vlan9) are serviced by dhcrelay.

I originally thought that this was a dhcrelay limitation, so I tried using
the wide-dhcp relay as well.  The same problem occurs, but with a useful
error message if I try and configure more than ten vlans:

 root at worm:~# relay -d vlan1 vlan2 vlan3 vlan4 vlan5 vlan6 vlan7 vlan8 vlan9
 ^C 
 root at worm:~# relay -d vlan1 vlan2 vlan3 vlan4 vlan5 vlan6 vlan7 vlan8 vlan9 vlan10
 relay[15320]: can't open bpf in open_if()
 root at worm:~#

It appears to me that there is a limit of ten bpf devices somewhere.  This
is backed up by what I see in dhcrelay.

So the question is how do I overcome this limitation?

In FreeBSD 4.x you used to specify the number of BPF devices in the kernel
configuration pseudo-device line.  That doesn't appear to be the case now.

I tried creating more BPF devices in /dev - I now have 80 /dev/bpf* entries,
but that didn't help.

Any assistance would be appreciated.

- Guy
-- 
Systems Manager, IT Division, Rhodes University, Grahamstown, South Africa
Email: G.Halse at ru.ac.za   Web: http://mombe.org/  IRC: rm-rf at irc.zanet.net
*** ANSI Standard Disclaimer ***                                   J.A.P.H