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Showing posts from November, 2009

Mastering Iptable Command Line Usage Linux Networking

Some of the most useful commands related to iptable,

To display filter table rules.#iptables -t filter -L

To display nat table rules.#iptables -t nat -L

To display raw table rules#iptables -t raw -L

To display mangle table rules.#iptables -t mangle -L

To delete all rules in the filter,nat,raw and mangle table.
#iptables -t filter -D
#iptables -t nat -D
#iptables -t raw -D
#iptables -t mangle -D

Set up IP FORWARDing and Masquerading
# iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
The above rule will do source nating.
( It will set eth0 IP address as source address for all outgoing packets on interface eth0.)
# iptables --append FORWARD --in-interface eth1 -j ACCEPT

Port forwading
# iptables -t nat -A PREROUTING -i eth0 -d --dport -j DNAT --to
The above rule will change the destinationIP:portnumber of the incoming packet to private.IP:portnum
Enabing the packet forward in the kernel with proc entry.
#echo 1 > /proc/sys/net/ipv4/ip_forward

iptables is a user space applica…