Understanding cause of DNS format error (FORMERR)

Gabriele Paggi gabriele.pgi at gmail.com
Sun Jun 24 04:10:21 UTC 2012

Hello Carsten,

> At Men&  Mice I've investigated this issue a few weeks ago for one of
> our customers. At that point of time, we've seen NS records with
> private addresses:
That's interesting but it still doesn't explain why BIND reports a 
format error in the reply it receives.
The reply is nonsense but it's legit and BIND should just return it. Am 
I wrong?
Beside that, I've been constantly getting a FORMERR reply for a week now.

> The issue seem to differ from the point in the network you are sending
> the query, and if the resolving DNS server has only IPv4 or is
> dual-stack (IPv4 + IPv6). It seems that the resolution is sometimes
> broken, but we have not found the root cause of the issue.
I'm running with only IPv4. May I ask you which version of BIND are you 
Jeffry is not able to reproduce the issue using BIND 9.9.1-P1 and I 
might consider an upgrade.

> We've also informed Microsoft about the issue.

I know what the answer is but I'll ask anyway: did you ever get a reply 
/ acknowledgement from them?



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