DHCP Multiple VLAN problem

john s e_z_now_peeps at hotmail.com
Fri Jul 20 06:28:46 UTC 2007

Hiya,Interesting, I will double check that, thanks for the pointer, I think I have just been looking at these options etc now for so many hours that I am bound to start missing stuff.Thanks for your help> Date: Fri, 20 Jul 2007 00:05:33 +0100> To: dhcp-users at isc.org> From: dhcp1 at thehobsons.co.uk> Subject: Re: DHCP Multiple VLAN problem> > Scott F wrote:> > >Basically we have 2 subnets set up in a shared network. One is for the> >VLAN1 data traffic and the other is for the VLAN 10 voice traffic. The> >DHCP Server is in VLAN1 and there is an IP Helpr set up to forward the> >DHCP traffic from VLAN1 to 10 (on the 3com 5500).> > OK, this is NOT a shared network then !> > >  On the VLAN 1 subnet> >all the computers are statically assigned addresses by MAC. I have set> >up two pools of addresses, one of VLAN1 range and the other on VLAN 10> >range. When the phones start up they are on VLAN1 and broadcast for an> >address, they get one along with other options that tell it that it> >should be on VLAN10, the phone releases its address and comes up on> >VLAN10 where it broadcasts and gets an address in the VLAN10 range,> >because the request comes from the helper, all seems to work ok.> >However, work want to have the pools set so people can't just plug in> >any device and get an address, but whenever I put any sort of> >conditional statement in DHCPd sees this as the most specific option> >and goes to the subnet containing it ignorning whether it has come by> >the helper or not.> > As I read it, you have incorrectly configured a shared network. VLANs > are not shared networks.> > I suspect that if you take out your shared network declaration then > things will work better. You will still need to identify the phones > when they first come up in VLAN1 (and give them the right config > options), but once they switch to VLAN10 then the server will have no > problem because it will know from the GIAddr field in teh relayed > packet that they are now on a different network.> 
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