Port forwarding in Linux

[Jared Buck]

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.

Jared

[David Hoffman]

On Sat, 12 Feb 2005 18:45:54 -0800, Jared Buck <JBuck814366460(a)aol.com&gt; 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

[Pedro Fernandes Macedo]

Jared Buck 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.
>
> Jared
>   
>  
You usually need to configure your router and your machine (in case you 
configured iptables on it).
For the iptables part , use what David Hoffman posted (may need some 
tweaking if you use NAT on the router).
For the router , you should check its manual for the specific details. 
It usually is something like:
- login in the router config interface (for linksys routers , it's a web 
interface on the router , with no username and password "admin" )
- go to the port forwarding option (some routers call this "virtual 
servers") (again , in linksys routers , this may be in the advanced 
settings)
- add the ports you want to forward and save the config

Be warned though.. Some routers cant handle fine the port forwarding 
rules.. My NetworkEverywhere (aka linksys) router gets too hot and needs 
some
reboots every two days since I added the port forwarding... (sadly , it 
seems like it's a normal problem with the model )

--
Pedro Macedo