How to configure Linux machine as router?

Here are some simple steps to do it, using Network Address Translation (NAT)

1. Enable packet forwarding . Make it permanent by adding “net.ipv4.ip_forward = 1” to /etc/sysctl.conf

   echo “1” > /proc/sys/net/ipv4/ip_forward

2. Enable iptables to handle NAT. ( eth0 is the public connection )

   /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

3. Save iptables settings

   service iptables save

4. Done. Check by routing table by verifying “netstat -nr” and iptables rules by “iptables -L”

This is a simple method for Redhat Enterprise Linux. See iptables docs for more detailed info.