I need to configure 2 NIC cards on single Ubuntu machine.. I will have to connect them to two different switches (in the same LAN) so as to compare and analyze the traffics over each of them..

What should I do in order to configure 2 NIC cards such that both of them should work at a time..?

I have tried it by editing-
sudo vim /etc/network/interfaces

and then-
sudo /etc/init.d/networking stop
sudo /etc/init.d/networking start

It then says-
networking stop/waiting
But Internet connectivity was still retained with the earlier IP address.. New settings were not being used even after restarting the service..
On the very next system reboot, Internet connectivity was found to be lost..Need help in this concern..