[Pdns-users] greater number of truncated replies with pdns_recursor?

Michael Loftis mloftis at wgops.com
Fri Mar 24 19:52:56 UTC 2006

--On March 24, 2006 11:37:24 AM -0800 Alan Hodgson <ahodgson at simkin.ca> 

> On March 24, 2006 11:15 am, "Tony Adams" <aadams at esnet.com> wrote:
>> This 'truncated' reply causes MS SMTP (IIS/Exchange) to retry the
>> request in TCP mode.  Now that I'm allowing TCP connections to my DNS
>> servers the behavior should cease.  I guess my question becomes, why
>> does the pdns recursor seem to produce more truncated replies than the
>> (presumably) bind server run by verizon ( to whom I was sending
>> recursive requests before I upgraded to pdns 2.9.20?
> precursor seems to return all the A records for the MX servers in the
> ADDITIONAL section, which is afak permitted, but does result in the
> result  packet exceeded 512 bytes and requiring TCP.
> I notice that dnscache does not do this, although it does receive and
> cache  the A records for future retrieval.   I don't have a BIND server
> handy to  try, but I would assume that your other recursor probably
> doesn't return  the A records when answering the recursive MX query.

BIND is only returning a couple of them (in a random or round robin 
fashion) in the ADDITIONAL section, filling the packet as close as it can 
to 512 bytes....

Earthlinks MX list is...huge.  AOL is very aware of these sorts of problems 
and you'll see they have about the same number of IPs in theirs, but they 
structure it so that you get less MX records and more A records to avoid 

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