Firewall DNS reverse- forward lookup
roger.ward at national-net.com
Thu Jan 1 16:07:18 UTC 2004
You are thinking backwards. It is reverse-forward, not
forward-reverse-forward that matters.
The reverse lookup's hostname must match a forward lookup for that IP.
Our mail servers, for instance, are mx1.mail.hostname.com, etc. The round
robin hostname for them is mx-rr.mail.hostname.com (and we have mx1 mx2
and mx3 sitting as round robin entries underneath that DNS record).
I don't use your firewall, but I have run across software which blocks
based on broken dns.
Make sure the PTR record for the IP address also has an A record with the
SAME IP address.
> Hello all,
> WE are having an issue with our Raptor firewall dropping packets because
> of a reverse - forward lookup fails. Here is the log and a link to why
> raptor logs it:
> "mw203.mail2world.com 126.96.36.199: reverse address 188.8.131.52
> doesn't match -- denied"
> My questions is : Is this a valid security check (reverse-forward)? Is
> there a problem with mail2world.com's DNS setup? Is Raptors' rule to
> just drop these connections valid? How would such a rule handle
> round-robin, where a forward lookup can return a a different IP? Or a
> number of IP's? Do any of you have any experience with this? TIA And
> happy new Year!!!.
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