EIGRP Summarization

• 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.