Common operational misconceptions

sthaug at sthaug at
Thu Feb 16 12:01:43 UTC 2012

> If you want to know if your resolver talks IPv6 to the world and
> supports 4096 EDNS UDP messages the following query will tell you.
> 		dig txt
> Similarly for IPv4.
> 		dig txt

Both PowerDNS recursor 3.3 and Nominum CNS 3.0.5 have problems
with these queries. They both get the TC answer from /
2001:4f8:0:2::8. Then:

- CNS tries with 4000 EDNS UDP size (4000 is the CNS documented max
UDP size), gets another TC.

- PowerDNS doesn't try to used EDNS at all.

Then they both try TCP and get a RST. And then they return SERVFAIL.

Steinar Haug, Nethelp consulting, sthaug at

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