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Re: Common operational misconceptions
From: sthaug () nethelp no
Date: Thu, 16 Feb 2012 13:01:43 +0100 (CET)

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 edns-v6-ok.isc.org txt

Similarly for IPv4.

              dig edns-v4-ok.isc.org txt

Both PowerDNS recursor 3.3 and Nominum CNS 3.0.5 have problems
with these queries. They both get the TC answer from 149.20.64.58 /
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 () nethelp no


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