DHCP server failover behind relay

[Glenn Satchell]

On Thu, September 6, 2012 8:06 am, Alex Bligh wrote:
>
>
> --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

How many remote subnets are there? If not too many then you could run an
ISC dhcrelay process on a system on each network, doesn't have to be the
gateway.

regards,
-glenn