[wellylug] Port Forwading

Jamie Dobbs jamie.dobbs at orcon.net.nz
Tue Jan 27 09:40:37 NZDT 2004


I have set up a Linux box to act as a router between two networks here at
work.
eth0 has IP 155.190.50.52 with a netmask of 255.255.255.0
eth1 has IP 203.110.12.230 with netmask 255.255.255.240

I want to route any traffic on port 5900 from equipment on eth0 to a
machine with IP 203.110.12.225 on eth1.

I have tried the following iptables entries (without success)

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 5900 -j DNAT
--to-destination 203.110.12.225:5900

iptables -t filter -A FORWARD -i eth0 -p tcp --dport 5900 -s 0/0 -d
203.110.12.225 -j ACCEPT

I was hopeful that someone could see any error I have made in these rules
that is stopping the IP forwarding from working.

(I have also remembered to "echo 1 > /proc/sys/net/ipv4/ip_forward", as I
have missed that before and spent houts trying to track down the cause of
my problems)




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