[dns-operations] Anycast vs. unicast NS

Simon Munton Simon.Munton at communitydns.net
Mon Mar 21 13:25:46 UTC 2011

> Anycast nodes should have a daemon that performs healthchecks against the nameserver daemon(s)

Hard to argue with that - the BGP take-down code is added complexity.

This also brings in issues like route flapping, if the checking code 
goes mad etc.

Of course, the unicast node will simply blackhole (or worst) queries 
when the DNS is not available, but the improved functionality is at a cost.

Totally agree with monitoring - much more complex with anycast.

A good example would be the probes we see from DNSMON - you'd like to 
think the spread would be pretty even, but in some cases we see one node 
hit by over a dozen probes.

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