Does anyone use anycast DHCP service?

Leo Bicknell bicknell at
Mon Aug 13 12:29:53 UTC 2012

In a message written on Mon, Aug 13, 2012 at 08:51:09AM +0000, Joe wrote:
> We are considering setup  reduant DHCP server clusers by using anycast.

I already see people pointing out problems with Anycast here, but
no one pointing out the best available solution.

Assuming your DHCP servers are properly clustered, simply have your
routers relay all requests to both servers.  Here's instructions
on setting up ISC DHCPD for redundant (pooled) servers:

Then configure your routers to send to both DHCP servers with
multiple helper-address lines:

interface Gig0/0
  ip helper-address
  ip helper-address

The way this work is when a box comes up the router sends DHCP
requests to both servers.  The DHCP server that reponds first will
be used by the client, which will complete negotiation with that
server via unicast.  The two DHCP servers will then synchronize
their pools.

Works great, no single point of failure, no anycast.

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 826 bytes
Desc: not available
URL: <>

More information about the NANOG mailing list