Rules for routing

The rules that you need to keep in mind when working with routes are:

Virtual routes must end in the subareas where the session end points reside.
Virtual route numbers must be defined the same in both directions but only at each end point. A virtual route definition does not need to be specified in every node in the path.
Explicit routes do not have to flow in both directions, but must be the same in one direction from endpoint subarea to endpoint subarea.
Explicit and virtual route rules apply in each network, not across SNI network boundaries.
Transmission group numbers on the VR that you are using must be the same in both directions, but only between two nodes, not along the entire path.