Down Interface, based on another interface's state.

[farsouth]

As the subject says, I am looking for a way to down interfaces (Wan connections) based on the state of another interface (lan connection)

We currently have 2 routers with wan interfaces. Web traffic is load balanced between them, but it can also be sent all down one side. When the lan connection fails, on 1 router, without downing the serial interfaces, we are unable to get all the traffic switched over to the other router.

So I am looking for a way that I can tie the state of one interface into the state of another interface.