DHCP relay with two interfaces

Bjorn Andersson bjorn at iki.fi
Wed Apr 25 06:33:39 UTC 2007

On 4/24/07, Carl Karsten <carl at personnelware.com> wrote:
> >
> > But then the server will reply to a 10.n.n.n address which is private,
> > and not routable.
> Why is it not routable?

Sorry, "not routable" was not the right expression, I meant not
*globally* routable, like the private addresses are. I may not have
control of the routing in the network between the DHCP server and the
DHCP relay. Packets between the DHCP relay and DHCP server must use
globally routable IPv4 addresses in the IP header.

> > And anyway, the criteria is that I am able to give
> > the same address to the same client independently of which network it
> > is in.
> I am not really sure what you mean by that.  Based on everything else you have
> said, do you mean:
> "the criteria is that I am able to give the same address to two clients that are
> in different networks "

If I have two clients, client A and client B, and two networks,
network 1 and network 2, then I want client A to get address x in both
network 1 and network 2 and client B to get address y in both network
1 and network 2.

I think I got it working well enough for my purposes by specifying one
subnet in the DHCP server configuration. I then set
the giaddr to the address of eth0 of my relay (which has a globally
routable address). I could also try David's suggestion.

I appreciate the answers and discussion. Thanks everyone.


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