View Remote IP Unicast FIB

In SPBM, each node has a System ID, which also serves as Backbone MAC address (BMAC) of the switch. The system populates these Backbone MAC addresses into the SPBM VLAN Forwarding Information Base (FIB). When the system discovers a network topology and stores it in the IS-IS link-state database, each node calculates shortest path trees for each source node, so that a unicast path now exists from every node to every other node. With this information, each node populates unicast information that it receives from SPBM into the FIB for forwarding purposes.

I-SIDs are only used for virtual services (Layer 2 VSNs and Layer 3 VSNs). If you only enable IP Shortcuts on the Backbone Edge Bridges, I-SIDs are never exchanged in the network as IP Shortcuts allows for Global Routing Table (GRT) IP networks to be transported across IS-IS.

The system adds the routes within the same VSN to the LSDB with a default preference of 7 and the inter-VSN routes with a route preference of 200. With IS-IS accept policies you can change the route preference for incoming routes. If the system learns the same route from multiple sources with different route preferences, then the routes are not equal cost multipath (ECMP) routes. The system prefers the route with the lowest route preference. In Layer 2, if there is a tie-break between routes from multiple sources, the tie-breaking is based on cost and hop count.