Understanding cause of DNS format error (FORMERR)

Sam Wilson Sam.Wilson at ed.ac.uk
Mon Jun 25 15:21:07 UTC 2012

In article <mailman.1121.1340625284.63724.bind-users at lists.isc.org>,
 Tony Finch <dot at dotat.at> wrote:

> It looks to me like this is an EDNS bug. ...

There's some kind of delegation bug as well.  If I query 
dns1[0-3].one.microsoft.com for SOA and NS for 
partners.extranet.microsoft.com you get sensible answers though the 
origin host is different for each server queried and those origins are 
privately addressed.

If I query dns1[0-3].one.microsoft.com for 
vlasext.partners.extranet.microsoft.com/IN/A I get answers with no AA 
bit set and a decreasing TTL as if the data were cached.  It does not 
appear that vlasext.partners.extranet.microsoft.com is delegated itself 
so it's not cached answers from a child zone.  The authority for 
zero-answer responses such as 
vlasext.partners.extranet.microsoft.com/IN/AAAA is the SOA for 

It's all rather horrible.


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