Linux configure Network Address Translation or NAT
Q. How do I configure Linux as a router to perform Network Address Translation (NAT) using iptables? I am using Cent OS.
A. NAT, also known as network masquerading, native address translation or IP-masquerading involves re-writing the source and/or destination addresses of IP packets as they pass through a router or firewall. Most systems using NAT do so in order to enable multiple hosts on a private network to access the Internet using a single public IP address. NAT is very popular because of IPv4 address shortage.
There are a few ways to set up a Linux machine to route. Iptables uses MASQUERADE targets. This is a special, restricted form of SNAT for dynamic IP addresses, such as most Internet service providers provide for modems or DSL.
Type following commands at shell prompt as root user:
# echo "1" > /proc/sys/net/ipv4/ip_forward
# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
# /etc/init.d/iptables save
# iptables -L
You can refer this previous article for more details.
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January 13th, 2007 at 10:42 pm
I would love to set up something I have seen Macs be able to do, internet connection sharing. My Mac has only one NIC but yet is able to share it by apparently binding a second alias (?) to that, run DHCP off the second addr range and NAT it. I haven’t seen anything that says exactly how do do this is linux (preferably Ubuntu). How can this be done?
September 1st, 2007 at 6:16 pm
You can do that with ‘aliasing’:
let the pc get its address from the ISP (will be on eth0). then, do a
ifconfig eth0:0 192.168.0.1
to set up a second subnet on the same network device. From here you can follow the normal instructions described above.