Sometimes we need to have multiple network connection in one time. Yep,,, I really need it right now. Because have no internet connection when work on site at client. So I brought my 3G modem for solving this problem. But make sure you route the connection between 2 network so it will runs both at the same time.I decide to set my modem priority higher than ethernet because I only need to connected to specific IP class. First thing to do is set modem network priority in System Preferences.

After that connect your first priority network, in my case is the 3G modem and plug the ethernet cable. After connected you can use internet connection but can’t work since it hasn’t routed yet. Open your terminal and logon as root (not user with root privileges) and type

netstat -nr

to show your routing table, you will get result similar like this :

If you see default interface used is ppp0 which is my 3G modem instead of ethernet. To make ethernet network connected you need to route it like this :

route add 172.16.xx.xx -netmask 255.255.255.0 172.16.xx.xx

After that check routing table again to make sure new routing information added. Now I can work by connected to ethernet network and still have internet connection from my modem