3.1.1 Ensure IP forwarding is disabled - sysctl

Information

The net.ipv4.ip_forward flag is used to tell the system whether it can forward packets or not. Setting the flag to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will never be able to forward packets, and therefore, never serve as a router.

Solution

Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file: net.ipv4.ip_forward = 0
Run the following commands to set the active kernel parameters: # sysctl -w net.ipv4.ip_forward=0 # sysctl -w net.ipv4.route.flush=1

See Also

https://workbench.cisecurity.org/files/1864