DHCP server failover behind relay

Vadym Abramchuk abramm at gmail.com
Wed Sep 5 21:08:48 UTC 2012

2012/9/5 Simon Hobson <dhcp1 at thehobsons.co.uk>

> Vadym Abramchuk wrote:
>  Unfortunally, none of my relay agents can send packets to both servers.
> So the proper fix is to get the vendor of the broken relay agent to fix it
> ;-)

My local supplier said it's not going to happen. At least before Second
Marsian War ends ;-).

>  As for broadcast, I've tried setting the relay's server address to
>> (broadcast of my servers subnet). dhcpd accepts DISCOVERs, but
>> the OFFERs do not reach the client.
> Where do they get lost ?
> Also it might help to describe your network topology.

Thanks for your replies, Simon.

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

>  Let's accept the axiom that I can't deliver requests to both servers. Is
>> there any other way?
> Not that I know of.
What about IPVS (Linux IP Virtual Server) and/or VRRP? I could bind both
DHCP servers to same virtual server IP and switch between them with
external failover.
The only question is disabling all isc-dhcpd's internal failover features
while still syncing databases.

Vadym Abramchuk
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