How to configure second ethernet card to communicate with intrenet marchine?

[Wenzhong Chen]

Hi all,
I am a newbie about linux. I try to set up a linux box as a router to the
internet. The linux box installed two network card. One is to connect to
internet. The other is connect to a intrenet subnet marchine. But when I
try to ping between them. It can't communicate with each other. The router
linux box's second ethernet card has a same subnet address(1.1.1.x) as the
intrenet marchine(1.1.1.x). But why they can't communicate? Even if in the
intrenet marchine I add the linux box as a router, it still can not work.
Who can help me? Thanks.

James