[CentOS] Forward all traffic from public IP A to public IP B?

Morten Sundstrøm morten at coretek.no
Mon Nov 3 21:44:48 UTC 2008


Need help.

Im trying to forward all traffic to a public server(A) to another public 
server(B) except traffic to port 22. Found this on google but cant get 
it to work. Could someone help me please.
Server A has one NIC server B has one NIC. Do i need 2 NICS in server A.

#!/bin/sh
iptables -F
iptables -F INPUT
iptables -F OUTPUT
iptables -F FORWARD
iptables -X
iptables -F -t nat
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD ACCEPT

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A PREROUTING -i eth0 --protocol tcp --destination-port 
! 22 -j DNAT --to-destination "IP B"
iptables -t nat -A PREROUTING -i eth0 --protocol udp -j DNAT 
--to-destination "IP B"
# END

/etc/rc.d/init.d/iptables status
Table: filter
Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

Table: mangle
Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination

Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination

Table: nat
Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination
1    DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0           tcp 
dpt:!22 to:"IP B"
2    DNAT       udp  --  0.0.0.0/0            0.0.0.0/0           to:"IP B"

Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination



/Morten.
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