[ale] iptables caching?

Stephen Cristol stephen at bee.net
Wed Dec 10 19:56:04 EST 2008


> I have the following rules in my iptables script:
>
>   $IPTABLES -A Allow --proto tcp --destination-port 25 -j ACCEPT
>   $IPTABLES -A PREROUTING -t nat -p tcp -i $IFACE --dport 25 -j DNAT
> - --to 10.1.1.34:25
>
>   $IPTABLES -A Allow --proto tcp --destination-port 80 -j ACCEPT
>   $IPTABLES -A PREROUTING -t nat -p tcp -i $IFACE --dport 80 -j DNAT
> - --to 10.1.1.32:80
>
> I had a typo originally that sent dport 80 to 10.1.1.32:25 which I
> fixed.  I have verified
> there are no other rules for port 80 but it is still sending anything
> that hits port 80 to
> 10.1.1.32:25.  The first 2 rules are working fine though.
>
> any ideas?


Make sure that the active rules are the rules you think are active with:

/sbin/iptables -vL
/sbin/iptables -t nat -vL

> If I had to guess, the issue lies in the Connection tracking in the
> kernel, not iptables itself.  I'm not sure how to clear this without a
> restart.

Often, watching the byte and packet counts in the verbose listing  
(above) are sufficient to identify what it happening. You can reset  
these counts with the -Z option.

If you need more information, you could also log packets.

S



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