Configuring Linux Machine As a Router(GATEWAY & ROUTERS)

Gateways and Routers

1.     Even though after subnetting individual network segments cannot communicate with each other, to configure a path for them we use router.

2.     Router is necessary for separate networks to communicate with each other, each network must be connected to a router in order for this communication to take place.

3.     This router that is connected to each network is called its gateway.

4.     In Linux, you can use a computer with two network interfaces to route between two or more subnets. To be able to do this you need to make sure that you enable IP Forwarding.

5.     You can check this by entering the following query at a command prompt:
cat /proc/sys/net/ipv4/ip_forward

6.     If forwarding is enabled, the number 1 is displayed; if forwarding is not enabled, the number 0 is displayed.

7.     To enable Ip forwarding if it is not already enabled, type the following command:
Echo “0” > /proc/sys/net/ipv4/ip_forward

Assume that a computer running Linux is acting as a router for your network, It has two network interfaces to the local LANs using the lowest available IP address in each subnetwork on its interface to that network.