Hai all,
I have configured Nat in this way , Actually i don't known meaning of this following line , can any tell me meaning of these.....


iptables --flush
iptables --delete-chain
iptables --table nat --delete-chain
iptables --table nat --append POSTROUTING --out-interface eth1 -j MASQUERADE
iptables --append FORWARD --in-interface eth2 -j ACCEPT


I am using two Ethernet card , one for getting internet from isp and another one for connecting to the Lan......

I don't how it works , tell me meaning of the above line......

well firstly you can find what these mean but reading the man page or other iptables documentation. Only the last two are actively related to nat, the first three just make sure there's nothing else already configured. so line 4 says that all traffic leaving eth1 is to have it's source address changed to the address configured on that interface, and the 5th line says that all traffic trying to pass through (so *through* the box, not *to* the box) the machine by entering on eth2 should be allowed, meaning it will then potentially be subjected to the logic in line 4.