Linux notes: Enabling IP Forwarding in Linux

In Linux, the IP forwarding function is not enabled by default. to confirm the status of the IP forwarding function, you can view the/proc file system and run the following command:
CAT/proc/sys/NET/IPv4/ip_forward

If the value in the preceding file is 0, IP Forwarding is prohibited. If the value is 1, IP Forwarding is enabled.

To enable the IP forwarding function, you can directly modify the above file:
Echo 1>/proc/sys/NET/IPv4/ip_forward

Change the file content from 0 to 1. If IP Forwarding is disabled, change 1 to 0.

The above command does not save the changes to the IP Forwarding configuration. The original value will still be used when the system starts the next time. To modify IP Forwarding permanently, You need to modify/etc/sysctl. modify the values of the following line in the conf file:
Net. ipv4.ip _ forward = 1

After modification, You can restart the system to make the modification take effect. You can also execute the following command to make the modification take effect:
Sysctl-P/etc/sysctl. conf

After the above configuration, the IP forwarding function will be permanently enabled.