DHCP server failover behind relay

[Alex Bligh]

--On 6 September 2012 00:08:48 +0300 Vadym Abramchuk <abramm at gmail.com> 
wrote:

> To simplify the things, here's a short cutoff: 10.0.0.70/24 is a primary
> DHCP server (running at present), 10.0.0.90/24 is secondary one
> (actually, it runs in virtual machine). Clients are at different subnet,
> 10.8.2.0/23. There's a L3 switch routing between subnets (Dell 6024F in
> this case), 10.0.0.1/24 at one side and 10.8.2.1/23 at another side. The
> switch acts as a DHCP relay.

How about run carp or similar on the 2 dhcp servers and use iptables
on each server with the -j TEE target (from memory) which will duplicate
the packet and send it to the other server. Clearly you'll want dhcp
listening on a loopback interface or something with the same IP number
on each server, and some proxy arp or similar to get the packet there.

-- 
Alex Bligh