6.7 Summarizing EIGRP Routes for IP
6.7.1 Classful boundary
EIGRP automatically summarizes routes at the classful boundary (the boundary where the network address ends as defined by class-based addressing). In some cases, however, you may not want automatic summarization to occur. If you have discontiguous networks, for example, you need to turn off summarization. To turn off automatic summarization, initiate the following command:

router(config-router)#no auto-summary

If you want to summarize networks in an address that you define, perform the following steps:

  1. Select the interface that will propagate the route summary.
  2. Specify the format of the route summary and the autonomous system into which it needs to be injected by using the following: 

    router(config-if)#ip summary-address eigrp as-number address mask

Lab Activity
  In this lab, you will learn how to discover Auto-Summarization by the EIGRP routing protocol.