[WBEL-users] OT iptables DNAT forwarding

[Ed Groth]

Daniel T. Gynn [Thu, Feb 26, 2004 at 12:52:03PM -0500]
> I know this is off topic, but I figured I'd give it a shot.
> 
> I am going crazy trying to forward pop3 requests to another server.
> Everywhere I see on the internet, it seems to be correct. If I access
> from an internal address, it seems to work, but from an external one, it
> just times out. My rules are:
> 
> $IPTABLES -A PREROUTING -t nat -p tcp --dport 110 -j DNAT --to $POP3
> $IPTABLES -A FORWARD -p tcp --dport pop3 -j ACCEPT
> 
> 
> I've even tried setting all rules to ACCEPT and it still won't work. Am
> I forgetting something?

Destination NAT only works when you're sure that all traffic passes
through the machine doing it.  I don't think you're making this mistake
but it's a common "gotcha" so I figured I'd mention it.

The other thing is that it looks to me like your iptables rules forward *all*
pop3 traffic destined to *any* host to your pop3 server _except_ when destined to
your machine.  You might want to add a destination host argument to the
PREROUTING command, and add an $IPTABLES -A INPUT -p tcp --dport pop3 -j ACCEPT. 
I'm not sure if the latter command is necessary, but you might try it.

Also, I havent played with iptables for a while and this might be completely
wrong! :v)

  Ed

> 
> 
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> Daniel T. Gynn
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