• Used specifically to minimize QUERY message domain
  • QUERY domain containment
    • Summarization
    • Stub router advertisement
  • QUERY message
    • Generated when route becomes Active
      • Active meaning node is asking if there’s another route to a destination.
      • Link loss
  • Auto Summary
    • Classful summarization
  • Manual Summary
    • Classless, defined by operator.
    • Supports any bit boundary.
    • Automatically suppresses subnet advertisements.
    • Can advertise subnets through leak-mapping.
    • Classic EIGRP
      • ‘ip summary-address eigrp’ under interface
    • Named EIGRP
      • summary-address at af-interface
  • EIGRP summaries are not hierarchical.
    • Can be done anywhere unlike OSPF.
  • Below is a config for EIGRP Named Mode:

Instead of going to the physical interface configuration, it’s all done in the address family af-interface config. On router R1, there’s a Loopback interface that has a /32.

But the EIGRP neighbor, R2, is receiving a /16 route to the loopback now.

  • Summary routes inherit metrics from the longer prefixes/subnets.
    • Will use the best metric.
      • Change of the best metric means the summary will be re-advertised.
      • summary-metric can help fix this.

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