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Route Summarization

Contents

  1. Example for Understanding Route Summarization
  2. Route Summarization and Route Flapping
  3. Requirements for Route Summarization

Chapter Description

In this sample chapter from CCNA 200-301 Portable Command Guide, 5th Edition, you will explore route summarization and requirements.

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CCNA 200-301 Portable Command Guide

CCNA 200-301 Portable Command Guide, 5th Edition

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Requirements for Route Summarization

To create route summarization, there are some necessary requirements:

  • Routers need to be running a classless routing protocol, as they carry subnet mask information with them in routing updates. (Examples are RIP v2, OSPF, EIGRP, IS-IS, and BGP.)

  • Addresses need to be assigned in a hierarchical fashion for the summarized address to have the same high-order bits. It does no good if Winnipeg has network 172.16.64.0 and 172.16.67.0 while 172.16.65.0 resides in Calgary and 172.16.66.0 is assigned in Edmonton. No summarization could take place from the edge routers to Vancouver.

TIP

Because most networks use NAT and the RFC 10.0.0.0/8 network internally, it is important when creating your network design that you assign network subnets in a way that they can be easily summarized. A little more planning now can save you a lot of grief later.

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