DHCP Relay agent not forwarding messages to the client

[Gero Palacio]

Hi Simon,

Thanks for the reply, I did not know if it was a bug or the correct
behavior.

If I may, let me ask you a follow up question. Does DHCP relay works well
with a pair of DHCP servers in failover mode?

I've configured the relay agent described in my previous email to forward
the messages to the pair of DHCP servers. Now everytime the relay agent
forwards a discovery message from the host, I receive 2 dhcp offers, one
from each server. As I've configured split to 128, only 1 server should
reply with an offer.

If I test the same configuration with hosts in the same subnet as the DHCP
servers, the behavior is as expected. The DHCP servers *responds or ignores*
the discovery messages according to the result of the hash based on the MAC
address of the hosts.

Any idea what might be the problem? Is it even a good idea to run a relay
agent and a pair of DHCP servers in failover?

Thanks!
Gerónimo.

On Mon, Jun 15, 2015 at 6:18 PM, Simon Hobson <dhcp1 at thehobsons.co.uk>
wrote:

> Gero Palacio <gero.palacio at gmail.com> wrote:
>
> > CLIENT <---> [eth0] (relay agent) ROUTER-1  [eth1] <---> ROUTER-2 <--->
> DHCP Server
> >
> > The relay agent runs ONLY on the interface that faces the client, which
> is eth0: "dhcrelay -4 -i eth0 10.0.1.10"
> ...
> > Can anybody tell me if I'm doing something wrong? Is this a known bug?
>
> It's a known feature. You must also listen on eth1 in order to get the
> replies from the server - it's just the way the relay agent works.
>
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