[plug] routing packets in iptables

Andrew Furey andrew.furey at gmail.com
Fri Apr 3 08:47:39 WST 2009

On 01/04/2009, Jon L. Miller <jlmiller at mmtnetworks.com.au> wrote:
> I'm trying to get my Blackberry Storm to pickup mail from our internal
>  server.
>  I'm needing some help in routing imap packets from a external internet
>  server with a iptables firewall running to an internal mail server.
>  What I have on the external server's firewall is:
>  EXT_IFACE = 'eth0'
>  $IPT -A FORWARD -p  tcp --dport 143 -j ACCEPT
>  $IPT -t nat PREROUTING -i $EXT_IFACE -p tcp --dport 143 -j DNAT
>  --to-destination [internal mail server]

It looks like you're missing a -A from that second, to actually add
the rule (is probably giving a syntax error) - so

$IPT -t nat -A PREROUTING -i $EXT_IFACE     etc.

Also, is the internal server's routing set to send the replies back
that way (eg having the external machine as the default gateway)? Just
something to think about depending on how complex your network setup


Linux supports the notion of a command line or a shell for the same
reason that only children read books with only pictures in them.
Language, be it English or something else, is the only tool flexible
enough to accomplish a sufficiently broad range of tasks.
                          -- Bill Garrett

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