sysctl -a 

sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 0

enable ip_forward setting to 1

sysctl -w net.ipv4.ip_forward=1

edit /etc/sysctl.conf to set permanently

vi /etc/sysctl.conf

add net.ipv4.ip_forward = 1

and then sysctl -p