linux NAT 配置实现上网

1、环境

[[email protected] ~]# lsb_release -a
LSB Version:    :core-4.0-ia32:core-4.0-noarch:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-ia32:printing-4.0-noarch
Distributor ID: CentOS
Description:    CentOS release 5.10 (Final)
Release:        5.10
Codename:       Final

[[email protected] ~]# getconf LONG_BIT
32

2.配置IP/DNS等信息

外网：

# ifconfig eth0 | grep "inet addr"
inet addr:222.47.48.25  Bcast:222.47.48.63  Mask:255.255.255.192

内网：

# ifconfig eth1 | grep "inet addr" 
inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0

DNS:

# cat /etc/resolv.conf
nameserver 222.47.62.142
nameserver 222.47.29.93

3.打开内核转发功能

echo 1 > /proc/sys/net/ipv4/ip_forward    //网卡重启后会恢复为0，所以需要把如下参数更改为“1”

# cat /etc/sysctl.conf | grep ip_forward
net.ipv4.ip_forward = 0

4.配置NAT

# iptables -t nat -A POSTROUTING -s 192.168.1.0/255.255.255.0 -o eth0 -j SNAT --to-source 222.47.48.25

# iptables -D FORWARD 1

# /etc/init.d/iptables save

# /etc/init.d/iptables restart