CCENT/CCNA ICND1 100-101 Official Cert Guide

Route Summarization and the IPv4 Subnetting Plan

For route summarization to work best, the IPv4 subnetting plan should be designed with route summarization in mind. Route summarization combines multiple routes into one route, but for that to work, the original routes must be in the same numeric range. That can happen by accident, but it works much better with planning. For example, Figure 21-1 shows a sample internetwork, with two sets of four subnets that could be summarized (some on the left, some on the right). Note that the subnetting plan placed subnets that begin with 10.2 on the left and those that begin with 10.3 on the right, which makes route summarization a little easier. To see why, focus on the right side for now, and ignore the ...