Production Line/Workcenter

Hello Gurus,

I had a question related to Production Line/Workcenter. I have a Material basically which can be build on two different Production lines, Production line 1 and Production line 2. While creating the Rate Routing though for this Material, I use Production line 1 as the workcenter. When I try to run Planning table, or Capacity, it only looks at Production line 1. How do I get Production line 2 in Planning table, which can be used for Capacity. Is their a way while creating Routing, that we can define a back-up (Production line2) for Production line 1, so that MRP/Planning table derives Capacity using both Production Line 1 and 2.

Is it done through Routing Alternate?? If yes how can we we set that MRP/Planning table looks for both Alternatives simultaneously.

Thanks in advance.

Sachin