[dns-operations] Sporadic but noticable SERVFAILs in specific dual stack nodes in an anycast resolving farm

Jeroen Massar jeroen at massar.ch
Wed Mar 5 14:15:22 UTC 2014

On 2014-03-05 14:45 , Kostas Zorbadelos wrote:
> The situation is described here:
> https://lists.isc.org/pipermail/bind-users/2014-March/092706.html

>From that post:
>> The main difference in the 3 machines from the rest is the IPv6
>> operation. Those machines are dual stack, having /30 (v4) and /127
>> (v6) on the physical interface.

As your queries are going outbound over IPv6 while the other boxes do
not, have IPv6, that is a big difference of course.

How exactly did you configure that /127 on the interface, you are aware
of this concept called subnet-router anycast address I hope?

As that could cause packets not to be able to exit once in a while in
miraculous ways...

Next to that see:

though some people disagree and thus there is now:

and thus:

Additionally, you might want to monitor address/route add/removals with
the 'ip mon' tool.


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