Configuring Multiple NETs for a Single IS-IS Process

Until recently, only a single IS-IS routing process could be enabled on a Cisco router. Even though only a single NET is required for an IS-IS process, multiple NETs can be configured for the same process by defining multiple NSAPs differentiated only by the Area IDs. This allows the router to multihome to the multiple areas defined, effectively merging the areas into a single area. During normal operation, for example, a Level 1 IS-IS router participates in flooding Level 1 LSPs throughout its home area. If this router connects to multiple areas, it also extends the flooding of Level 1 LSPs between those areas, effectively merging them. An example of a multihomed configuration is shown in ...

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