Port forwarding in Linux

[David Hoffman]

On Sat, 12 Feb 2005 18:45:54 -0800, Jared Buck <JBuck814366460 at aol.com> wrote:
> I need a little assistance here.
> 
> One of my friends tells me the reason Bittorrent is downloading so
> slowly is because a certain group of ports isn't open.  I do not know
> how to open ports in Linux.  I can tell you my computer is connected to
> the Internet through a DSL router since everyone in my family uses DSL.
> 
> Could someone tell me how to open up the required ports?  I looked
> through the archives and there's no record of a question of this type
> being asked.
> 

Try google too.

Here are my rules:

intip=172.1.2.3 (the IP address of your ethernet port coming in from outside)
destip=192.168.x.x (the IP address of the machine on your internal network)
iptables -t nat -A PREROUTING -d $intip -p tcp --dport 6881:6999 -i
eth1 -j DNAT --to-destination $destip
iptables -t nat -A PREROUTING -d $intip -p udp --dport 6881:6999 -i
eth1 -j DNAT --to-destination $destip
iptables -t nat -A PREROUTING -d $intip -p tcp --dport 6346 -i eth1 -j
DNAT --to-destination $destip
iptables -t nat -A PREROUTING -d $intip -p udp --dport 6346 -i eth1 -j
DNAT --to-destination $destip