Anycast DNS

[sthaug at nethelp.no]

> > Have seen some anycast DNS implementations using more than one address,
> > some times even on the same subnet, any considerations or reasons for
> > doing that?
> 
> We do that.
> 
> We use two different, indepentent methods to route traffic to the IPs. 
> We feel this provides a greater degree of resilience.

More than one address also lets you do some load balancing or traffic
steering, if that is desirable.

(E.g.: Anycast group 1 announces prefix 1 with localpref 110, prefix 2
with localpref 120. Anycast group 2 announces prefix 1 with localpref
120, prefix 2 with localpref 110.)

Steinar Haug, Nethelp consulting, sthaug at nethelp.no