full-disclosure - Fw: [NTBUGTRAQ] Win 2003 DNS requests makes replies over 512 byte PIX limit

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From: dbt at meat.net (David Terrell)
Subject: Fw: [NTBUGTRAQ] Win 2003 DNS requests makes replies over 512 byte PIX limit

On Fri, May 09, 2003 at 09:47:01AM +0100, John.Airey@...b.org.uk wrote:
> I've mentioned this issue before on this list (see the thread "SQL Slammer -
> lessons learned"), but I'll repeat it again. Your internal resolver only
> needs to connect to port 53 of external machines to send email to them. The
> connection back to your machine will be on a higher port. The Pix will use
> stateful filtering to allow the connection to the higher port (ie it detects
> that the connection was originated from the inside).
> 
> Try "show conn prot udp" (or "show conn") on the firewall to see where the
> connections are really going. Even "netstat -a" on the server should give
> you some information about connections.

'protocol fixup dns 53' (from memory, I fortunately no longer admin
PIX firewalls for a living...) would affect both incoming and
outgoing DNS packets, regardless of what the outgoing query port
was...

-- 
David Terrell            |
Prime Minister, NebCorp  | Gary Hart for President!
dbt@...t.net             |  http://www.garyhartnews.com/hart/
http://wwn.nebcorp.com   |