EIGRP Building Blocks

Now that you have a functioning EIGRP topology, you can quickly review how EIGRP operates to get the necessary background to troubleshoot it efficiently. This section is designed to give you enough information about EIGRP to complete the lessons in this chapter. For an in-depth description of any concept in this chapter, refer to the Cisco IOS IP and IP Routing Protocols Configuration Guide for your particular Cisco IOS software version. Another excellent source of information on both IGRP and EIGRP is Routing TCP/IP, Volume I by Jeff Doyle (Cisco Press, 1998).

Packet Formats

EIGRP uses five different packet types:

  • Hellos/acknowledgments— Hellos are the multicast neighbor discovery/recovery mechanism used by EIGRP. A hello ...

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