Summarization
Chapter 1, "Hierarchical Design Principles," stated that network stability is dependent, to a large degree, on the number of routers affected by any change. Summarization hides detailed topology information, bounding the area affected by changes in the network and reducing the number of routers involved in convergence.
In Figure 2-2, for example, if the link to either 10.1.4.0/24 or 10.1.7.0/24 were to fail, Router H would need to learn about these topology changes and participate in convergence (recalculate its routing table). How could you hide information from Router H so that it wouldn't be affected by changes in the 10.1.4.0/24, 10.1.5.0/24, 10.1.6.0/24, and 10.1.7.0/24 links?
Figure 2-2. Hiding Topology Details from a Router ...
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