DHCP server failover behind relay

Alex Bligh alex at alex.org.uk
Thu Sep 6 21:48:38 UTC 2012

--On 6 September 2012 22:47:00 +0100 Alex Bligh <alex at alex.org.uk> wrote:

>> Just tried -j TEE and got the local loop with two servers copying packets
>> to each other :(.
>> Any idea on how to avoid this? TTL check looks weird.
> Set two servers up each with a loopback address of W.X.Y.Z. Use that
> address in the relay agents, and for dhcp to listen on. When you do
> the -j TEE, also set some other marker on the packet (I'd suggest the
> tos field - see --tos and --set-tos) to prevent looping.

Or perhaps easier, use --mac-source as a qualification to the -j
command to match the router (or exclude the other server).

Alex Bligh

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