Please note the following IP config I will be using
Replace xx.xx.xx.xx with your WAN IP
Replace yy.yy.yy.yy with your LAN IP
(i.e. 192.168.0.0/16, 172.16.0.0/12)
WAN = eth0 with public IP xx.xx.xx.xx
LAN = eth1 with private IP yy.yy.yy.yy/ 255.255.0.0
First you nee dto install the NIC's Into your linux system. Once you have done this you will need to verify they are installed correctly. To do this type the following command
[root@yourRouter ~]# ls /etc/sysconfig/network-scripts/ifcfg-eth* | wc -lIf you have the NIC's Installed correcly the output of this command will be 2.
Now we must give eth0 [The Primary Ethernet Card] An external WAN IP. This will be provided to you by your ISP.
To do this type the following command
[root@yourRouter ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0You must make the file look similar to the configuration I have shown below
DEVICE=eth0 BOOTPROTO=none BROADCAST=xx.xx.xx.255 # Optional Entry HWADDR=00:50:BA:88:72:D4 # Optional Entry IPADDR=xx.xx.xx.xx NETMASK=255.255.255.0 # Provided by the ISP NETWORK=xx.xx.xx.0 # Optional ONBOOT=yes TYPE=Ethernet USERCTL=no IPV6INIT=no PEERDNS=yes GATEWAY=xx.xx.xx.1 # Provided by the ISPNow we have configured the eth0 card we must configure eth1 to have an INTERNAL IP Address. To do this type the following
[root@yourRouter ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth1Similar to above make the configuration look like the one below
BOOTPROTO=none PEERDNS=yes HWADDR=00:50:8B:CF:9C:05 # Optional TYPE=Ethernet IPV6INIT=no DEVICE=eth1 NETMASK=255.255.0.0 # Specify based on your requirement BROADCAST="" IPADDR=192.168.2.1 # Gateway of the LAN NETWORK=192.168.0.0 # Optional USERCTL=no ONBOOT=yesNow we need to configure the host file to tell the Router that it will be providing Network Address Translation [NAT]
[root@yourRouter ~]# vi /etc/hostsYour hosts file should look like this
127.0.0.1 nat localhost.localdomain localhostNow we configure the gateway by editing /etc/sysconfig/network to do this use the vi command
[root@yourRouter ~]# vi /etc/sysconfig/networkYou should make it similar to this :
NETWORKING=yes HOSTNAME=nat GATEWAY=xx.xx.xx.1 # Internet Gateway, provided by the ISPNow we need to configure the Resolver to do it use the vi command like so
[root@yourRouter ~]# vi /etc/resolv.confMake that file like the one below. these IP's may differ from yours.
nameserver 188.8.131.52 # Primary DNS Server provided by the ISP nameserver 184.108.40.206 # Secondary DNS Server provided by the ISP
Now we must clean up our iptables.
Start off by flushing them
[root@yourRouter ~]# iptables --flush [root@yourRouter ~]# iptables --table nat --flush [root]@yourRouter ~]# iptables --delete-chain
Now we need to delete all the chains not in the default filter and the NAT
[root@yourRouter ~]# iptables --table nat --delete-chain
Now we need to configure IPTABLES to allow routing
to do this type
[root@yourRouter ~]# iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE[root@yourRouter ~]# iptables --append FORWARD --in-interface eth1 -j ACCEPT
Now we need to enable packet forwarding by the Kenrel
[root@yourRouter ~]# echo 1 > /proc/sys/net/ipv4/ip_forward
Now we can apply our new configuration
[root@yourRouter ~]# service iptables restart
Now ping some places from your client and see if it works