Chapter 3
1: | How many levels of hierarchy does the IS-IS routing protocol support and what is their significance? |
A1: | Two levels, Level 1 and Level 2, are specified by ISO 10589 and adopted by RFC 1195. Hierarchical routing allows control over the spread of routing updates, which is a key requirement for network stability and scalability. |
2: | What is the reason for suboptimal interarea routing in the ISO 10589 architecture? |
A2: | In the ISO 10589 architecture, the Level 1 routing areas are stubs and do not have a complete view of the domain that is necessary for making optimal exit decisions out of their local area. Instead, Level 1 routers point defaults to the nearest Level 2 router, which might not necessarily be on the best path to a specific destination ... |
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