Corosyn for DHCP failover

[Frank Bulk]

The appliance we use does iptables to mangle the packets.  We had this same
issue with a piece of access gear that requires the source IP of the DHCP
responses to match the IP address it relayed it to.

Frank

-----Original Message-----
From: dhcp-users-bounces+frnkblk=iname.com at lists.isc.org
[mailto:dhcp-users-bounces+frnkblk=iname.com at lists.isc.org] On Behalf Of
Glenn Satchell
Sent: Tuesday, June 07, 2011 8:13 AM
To: Users of ISC DHCP
Subject: Re: Corosyn for DHCP failover

On 06/07/11 21:47, neeraj jain wrote:
> Hi all,
> I am tring to use the corosync for the dhcp failover instead of DHCP
> failover configuration. I am able to run the dhcp with the corosync
> successfully and tested the failover also. Corosync assign the VIP and
> switch in case of failover. I am also using rsync to synchronize the
> configurations and lease file.
> Only problem is that when my relay agent send the DHCP discover request
> at VIP, my dhcp server reply with offer using the physical ip of the
> machine.
> What I need is the discovery and offer should happen at the same VIP. I
> am not sure why DHCP is using physical ip to reply for the request.
> Even I am not sure if this the correct forum to raise this question but
> help me in case someone has faced the same problem.
> Thanks in advance,
> Neeraj jain
>
>

Hi Neeraj

Depending on your operating system, the usual behaviour for any socket 
is to use the first IP assigned on that interface as the source address.

You can override this to some extent using the 'server-identifier' 
setting in dhcpd.conf. See the man page for full details.

Note that this doesn't necessarily change the source IP address of 
packets from the server, but it sets an internal dhcp option so that the 
client will use this address when contacting the server.

-- 
regards,
-glenn
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