port address translation

Mark_Andrews at iengines.com Mark_Andrews at iengines.com
Mon Nov 29 12:16:48 UTC 1999

	While he has got the port number wrong (it should be 53
	for DNS) what he is saying about IP filtering rules is

	If you advertise a nameserver to the world you are expected
	to accept DNS queries from ANY port (both TCP and UDP) not
	just port 53.


> I got this from the admin at another site that can't see my site. When
> one of their users tries to get to my site (mail, www, ftp), it's like
> it is completely down. Their traceroutes to us go nowhere, and we see
> no packets coming in from them. Noone else has this problem getting to
> my site. I run BIND 4 on Solaris. I run dns on 53 and smtp on 25.
> What RFCs is this guy talking about? I looked through them, and nothing
> seemed to apply.
> > The problem is that we do PAT on our firewall and when you request a
> dns
> > resolution to zzz.com it sends the request out with a src port of
> > anywhere between 5000-65000. Standard DNS request are normally src'ed
> with
> > port 25. It is apparent that zzz.com considers dns request src'ed with
> > anything but port 25 a security risk. This is the same Issue that we
> had
> > with apple.com, worldcom.com...at that time it was
> > considered an issue with the vendors and if they chose not to comply
> with
> > RFC's that govern PAT protocol it would be their choice.
> * Sent from RemarQ http://www.remarq.com The Internet's Discussion Network *
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Mark Andrews, Internet Engines Inc. / Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at iengines.com

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