How to enable IP Forwarding in Linux
Check if IP Forwarding is enabled
sudo sysctl net.ipv4.ip_forward
if the output value is 1, it means it is on. otherwise, we move on to the next step.
Enable IP forwarding
Temporary enable
sysctl -w net.ipv4.ip_forward=1
Permanent enable
open the file /etc/sysctl.conf, use your favourite text editing tool.
sudo emacs /etc/sysctl.conf
add the following line. and save and exit.
net.ipv4.ip_forward=1
save ip forwarind in kernel.
sysctl -p