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It depends on what kernel version you are using. With 2.4 you can choose between doing postrouting or the easier prerouting. The difference is if you do a postrouting, all clients within your internal network (LAN) can connect and download/upload between each other. Postrouting is not necessary if you are the only client which uses DC behind the router/firewall. The examples below use the following settings: External Ethernet card: eth1, external IP 213.112.8.55, firewall (router) IP: 192.168.0.1, client IP: 192.168.0.2, external and internal port: 555

 

Linux 2.4, postrouting example

iptables -t nat -A POSTROUTING -d 192.168.0.2 -s 192.168.0.0/24 -p tcp --dport 555 -j SNAT --to 192.168.10.1

iptables -t nat -A POSTROUTING -d 192.168.0.2 -s 192.168.0.0/24 -p udp --dport 555 -j SNAT --to 192.168.10.1

iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 555 -j DNAT --to 192.168.10.2:555

iptables -t nat -A PREROUTING -i eth1 -p udp --dport 555 -j DNAT --to 192.168.10.2:555

iptables -t nat -A PREROUTING -d 213.112.8.55 -p tcp --dport 555 -j DNAT --to 192.168.10.2:555

iptables -t nat -A PREROUTING -d 213.112.8.55 -p udp --dport 555 -j DNAT --to 192.168.10.2:555


Linux 2.4, prerouting example

iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 555 -j DNAT --to 192.168.0.2:555

iptables -t nat -A PREROUTING -i eth1 -p udp --dport 555 -j DNAT --to 192.168.0.2:555

 

Linux 2.2, example

ipmasqadm portfw -a -P tcp -L 213.112.8.55 555 -R 192.168.0.2 555

ipmasqadm portfw -a -P udp -L 213.112.8.55 555 -R 192.168.0.2 555

Submitted by tajisen

 

How to use Shorewall to configure your iptables

Here's what you have to add to rules (assuming loc is the zone where your computer is located, 192.168.0.7 is your computer's IP, 666 is the port you wish to use and 123.45.67.89 is your external IP):

#ACTION
SOURCE
DEST
PROTO
DEST PORT
SOURCE PORT(S)
ORIGINAL DEST
DNAT
net
loc:192.168.0.7
tcp
666 -
123.45.67.89
DNAT
net
loc:192.168.0.7
udp 666 -
123.45.67.89

Submitted by Ender



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by USR56K See Profile edited by JMGullett See Profile
last modified: 2007-01-29 16:02:51