IP Forwarding in Router
What is IP Forwarding in a router? How to configure it in a router?
IP forwarding refers to passing of IP packets between hosts with the help of routers. It has to be done as soon as possible on routers or on PCs itself. IP forwarding can be done in IP network only where a data link layer network is connected with other data link layer via a router. IP forwarding on router makes use of routing tables for the transmission of IP packets. A routing table helps the router to process a packet to its destination address. IP forwarding can be enabled or disabled. If it is enabled, then the IP datagram received is sent to a different system other than the local system. The router processes the IP datagram for its header validation, routing table lookup, decrement TTL, etc.
Following are the methods to configure IP forwarding on a router and points to remember:
- Using Forwarding option
- Enable IP forwarding
- Points to remember
Using Forwarding option
The functions of a router is to forward the request that goes through the router to the web server. If the IP forwarding is not configured, the router stops the HTTP request. The computer should have a static IP address. At 'My Network Places' option on the 'Desktop', you check the settings by selecting the 'Properties' option. The default gateway IP address must be the same as that of the router’s internal IP address. Firstly, you need to check if the router supports IP forwarding. You have to start the browser and type the router’s IP address in the address bar of the browser. Then, enter username and password and select the 'Advanced' tab. Click the 'Forwarding' tab and enter 80 in the port. Then enter the IP address of the required server. You can create another port to enable other features like Windows Media Streaming which has the default port as 81.
Enable IP forwarding
Checking the IP forwarding’s current status on IPv4 IP class is by the use of the command line - '# cat /proc/sys/net/ipv4/ip_forward' or '# cat /etc/sysctl.conf | grep net.ipv4.ip_forward'. To enable the IP forward option directly from the terminal, use command lines like '# echo 1 > net.ipv4.ip_forward = 1', and '# sysctrl -w net.ipv4.ip_forward=1'. These command lines when executed take effect immediately.
If IP forwarding is disabled, then change its numerical value setting to 1 from 0 to enable the IP forwarding option. You can test the port forwarding from the Internet other than testing inside the router itself. You can use the port check tool for testing port forwarding. The computer must have static assigned IP address. Rebooting the router allows Ip forwarding to take effect immediately.
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