CCNA 200-301 Portable Command Guide, 5th Edition

Chapter 4. Route Summarization

This chapter provides information concerning the following topics:

• Example for understanding route summarization

• Route summarization and route flapping

• Requirements for route summarization

Route summarization, or supernetting, is needed to reduce the number of routes that a router advertises to its neighbor. Remember that for every route you advertise, the size of your update grows. It has been said that if there were no route summarization, the Internet backbone would have collapsed from the sheer size of its own routing tables back in 1997!

Routing updates, whether done with a distance-vector protocol or a link-state protocol, grow with the number of routes you need to advertise. In simple terms, a router that ...