Does -o and -i make sense on these rules?

yzT! · 09-16-2014, 06:00 AM

Code:

iptables -A FORWARD -s 192.168.20.7 -d 10.10.48.3 -p tcp --dport 25 -o eth1 -j ACCEPT
iptables -A FORWARD -s 10.10.48.3 -d 192.168.20.7 -p tcp --sport 25 -i eth1 -j ACCEPT

Tuning the firewall of my organization I found these two lines which confuse me. The eth1 interface is connected to the 10.10.x.x network and eth0 to 192.168.x.x, so... does it make sense to put the -o eth1 and the -i eth1 if that is already implied by the -d 10.10.48.3 and -s 10.10.48.3, respectively?

GunFighT · 09-22-2014, 02:45 AM

In the 1st rulle:
"-o" parameter, tells that from -s (source IP/subnet) goes to -d (destination IP), on eth1. The "-o" is like a output rulle. Forces all traffic from source IP to destination IP, to go on eth1.

kaushalpatel1982 · 09-22-2014, 03:32 AM

yzTi, it is not require in this case.