IS-IS: Deployment in IP Networks

Neighbor Relationships and Pseudonodes on Broadcast Networks

Broadcast networks pose special scaling and efficiency problems for link state protocols. We'll use the network illustrated in Figure 2-13 to illustrate this.

Figure 2-13. IS-IS routers on a broadcast network

In this network, under normal circumstances, the intermediate systems would need to build a number of adjacencies across the common broadcast network:

• Router A to routers B, C, and D

• Router B to routers A, C, and D

• Router C to routers A, B, and D

• Router D to routers A, B, and C

For each of these adjacencies, the link state databases would need to be synchronized—four sets of CSNPs would ...