Two subnets in DHCP Server

Karl Auer kauer at
Thu Sep 3 11:16:13 UTC 2009

On Thu, 2009-09-03 at 11:16 +0200, Florian Diesch wrote:
> Stephan Schöffel <schoeffel at> writes:
> > I'm trying to make my dhcp server provide addresses for two subnets. It 
> > works well for the first, but not on the second.
> [...]
> > The server address is Does it have to have another NIC in 
> > the net?
> Yes. 

No :-)

*Something* has to have a NIC in the second subnet. You can have a
second NIC on the server itself, attached to the second subnet, in which
case the server can listens directly for incoming requests.

Alternatively, you can put a DHCP relay on some other machine in the
second subnet, configured to forward DHCP requests to your DHCP server.
Obviously the "some other machine" can't be getting an address via DHCP!

If your subnets are on a commodity router, it is very likely that the
router has DHCP relay functionality built in, and you only need to turn
it on. If you are using a Ubuntu box or similar as a router, you will
most probably find DHCP relay software in the repositories.

Regards, K.

Karl Auer (kauer at                   +61-2-64957160 (h)                  +61-428-957160 (mob)

GPG fingerprint: 07F3 1DF9 9D45 8BCD 7DD5 00CE 4A44 6A03 F43A 7DEF

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