Summary

This chapter is important to your overall understanding of routing metrics and distances. You need to understand the topics discussed in this chapter to be able to progress from here. You learned about convergence, which is the process that routers go through when a route has become unavailable. The primary activities of convergence are update, invalid, holddown, and flush. You also learned about parallel paths, the effect of parallel paths on convergence, the effect of parallel paths on packet forwarding, and how to review parallel paths in a routing table. The difference between process switching and fast switching was also discussed.

This chapter has touched upon the role of split horizon, including what it means for routing advertisements with split horizon enabled and disabled. Finally, IGRP routing metrics (variables) and Cisco administrative distances were explained. Chapter 3, "Discontiguous Networks, Summarization, and Subnet 0," continues the discussion by delving deeper into these topics.