[root@ns1 sysconfig]# vi iptables

#なんも入ってないです。

:q!

[root@ns1 sysconfig]# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

[root@ns1 sysconfig]# service iptables save

[root@ns1 sysconfig]# /etc/init.d/iptables restart

Flushing all current rules and user defined chains:            [  OK  ]
Clearing all current rules and user defined chains:            [  OK  ]
Applying iptables firewall rules:                              [  OK  ]
                                                               [  OK  ]

[root@ns1 sysconfig]# /etc/init.d/iptables status

Table: filter
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
Table: nat
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
MASQUERADE  all  --  anywhere             anywhere

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

Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination


[root@ns1 sysconfig]# vi iptables

# Generated by iptables-save v1.2.10 on Thu Feb 26 02:17:15 2015
*mangle
:PREROUTING ACCEPT [2363:613830]
:INPUT ACCEPT [2363:613830]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [39378:18230296]
:POSTROUTING ACCEPT [39378:18230296]
COMMIT
# Completed on Thu Feb 26 02:17:15 2015
# Generated by iptables-save v1.2.10 on Thu Feb 26 02:17:15 2015
*nat
:PREROUTING ACCEPT [26:1492]
:POSTROUTING ACCEPT [5:300]
:OUTPUT ACCEPT [5:300]
[0:0] -A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu Feb 26 02:17:15 2015
# Generated by iptables-save v1.2.10 on Thu Feb 26 02:17:15 2015
*filter
:INPUT ACCEPT [2363:613830]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [39378:18230296]
COMMIT
# Completed on Thu Feb 26 02:17:15 2015

:q!