다음과 같은 외부와 연결시키고 싶은 네트워크가 있다고 하자.

   _____________
  /                     \               외부 IP               _________              내부 IP
 |   Internet          |           123.12.23.43           |  linux     |          192.168.0.1
 |   google.com    | ------[외부 랜카드]------| machine |------[내부 랜카드]
  \_____________/                                         ----------             |
                                                                                               |        
                                                                                               |
                                                   _____________                ______|_______
                                                  | 192.168.0.2  |             /                      |
                                                  |    내부        |--------|    192.168.0.0    |
                                                  |    컴퓨터     |            |      인트라넷      |
                                                  --------------             \______________/ 

외부 네트워크 카드는 eth0, 외부 IP는 123.12.23.43, 그리고 내부 네크워크 카드는 eth1라고 가정하자.

$> modprobe ipt_MASQUERADE # 만약 실패하더라도 다음을 계속하시오.


$> iptables -F; iptables -t nat -F; iptables -t mangle -F


$> iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 123.12.23.43


$> echo 1 > /proc/sys/net/ipv4/ip_forward

그리고 보안을 위해:

$> iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


$> iptables -A INPUT -m state --state NEW -i ! eth0 -j ACCEPT


$> iptables -P INPUT DROP  # 위의 두 줄이 성공한 경우에만


$> iptables -A FORWARD -i eth0 -o eth0 -j REJECT

이 문서는 GNU Free Documentation License를 따른다.

http://www.gnu.org/copyleft/fdl.html