Anycast DNS

[Phil Mayers]

On 01/03/12 03:40, Beavis wrote:
> Just want to piggy back on this topic is there any documentation
> available online that shows a deployment guideline for Anycast?

There's not much to it:

  1. Create the anycast IP on your servers
  2. Route the anycast IP to your servers
  3. Make bind listen on the anycast IP

1 & 3 are easy.

2 can be accomplished using a very wide variety of methods. We use BGP, 
with a locally-created BGP speaker that checks port 53 for a reply and 
advertises/withdraws the route dynamically, but exabgp would be my 
recommendation, since it has a built-in facility to announce/withdraw 
routes via a "watchdog" script - see pages 5 & 6 of:

http://thomas.mangin.com/data/pdf/Linx%2074%20-%20Mangin%20-%20BGP.pdf

Alternatively you could use OSPF with Zebra/Quagga/Whatever. For example:

http://www.digriz.org.uk/ha-ospf-anycast

Cisco IP SLA probes, with "track" static routes are another option.

Or, if you don't care about dynamically withdrawing the route when bind 
goes away, just plain static routes.