Other Factors in IS-IS Scaling

There are at least four protocol structure factors that need to be considered when working with IS-IS: SPF flooding, the number of pseudonodes allowed in an area, the possibility of overrunning the IS-IS database on a given router, and metrics.

Link State Flooding

One of the major factors to consider when you're using any link-state protocol is the amount of flooding that occurs, since excessive flooding can cause CPU utilization and memory usage.

IS-IS in an IP network has an immediate advantage because it treats all IP reachability information as leaf nodes in the shortest path tree. Because of this, any change in IP reachability information is always only a partial shortest path first (SPF) run—the leaf nodes ...

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