I don’t know when exactly this setting change. A year ago I put a syntax in /etc/rc.local to check whether the ip_foward setting is 1 or 0 but force it to 1. The command I used is
#cat 1 > /proc/sys/net/ipv4/ip_forward
For the last 2 days it returned to 0 again. I thought the internet went down because the virus in some laptop attacking the network. But today I found out the ip_forward setting is 0.
I just found out that the ip_forward is very essential to a computer act as a server. One of the effect is my pidgin in client computer can’t connect. I still can browsing. While the other notebook can’t have their ip on the network.
So I must do the cat command again to activate it or doing something different like this website suggested. Thanks for the owner.
Check the parameter in /etc/sysctl.conf for ip_forward
#sudo grep ip_forward /etc/sysctl.conf
If result in net.ipv4.ip_forward=1 go to this command
#sudo sysctl -p /etc/sysctl.conf
That’s it. Otherwise change the parameter in sysctl.conf into 1.