The following figure shows the SPB domain interconnect configuration.
In this is scenario, two SPB domains are connected by PIM Gateway
interfaces, and there is no traditional PIM Network involved. The
Controllers from each SPB domain form MSDP adjacencies the Controllers
in the other domain (but not within the same domain) other to share
their multicast sources. The SPB-PIM Gateway nodes see the other SPB-PIM
Gateway nodes as PIM neighbors on the SPB-PIM Gateway interfaces.
