Unlike IGRP, which is a classful routing protocol, EIGRP supports classless interdomain routing (CIDR), allowing network designers to maximize address space by using CIDR and variable-length subnet mask (VLSM). Compared to IGRP, EIGRP boasts faster convergence times, improved scalability, and superior handling of routing loops.

Furthermore, EIGRP can replace Novell Routing Information Protocol (RIP) and AppleTalk Routing Table Maintenance Protocol (RTMP), serving both IPX and AppleTalk networks with powerful efficiency.

EIGRP is often described as a hybrid routing protocol, offering the best of distance vector and link-state algorithms.

EIGRP is an advanced routing protocol that relies on features commonly associated with link-state protocols. Some of the best features of OSPF, such as partial updates and neighbor discovery, are similarly put to use by EIGRP. However, EIGRP is easier to configure than OSPF.

EIGRP is an ideal choice for large, multi-protocol networks built primarily on Cisco routers.

This module covers common EIGRP configuration tasks. Particular attention is paid to the ways in which EIGRP establishes relationships with adjacent routers, calculates primary and backup routes, and when necessary, responds to failures in known routes to a particular destination.

A network is made up of many devices, protocols, and media that allow data communication to happen. When one piece of the network does not work properly, one or two users may be unable to communicate, or the entire network may fail. In either case, the network administrator must quickly identify and troubleshoot problems when they arise. Network problems commonly result from the following:

• Mistyped commands
• Incorrectly constructed or incorrectly placed access lists
• Misconfigured routers, switches, or other network devices
• Bad physical connections

A network administrator should approach troubleshooting in a methodical manner, using a general problem-solving model. It is often useful to check for physical layer problems first and then move up the layers in an organized manner. Although this module will focus on troubleshooting the operation of routing protocols, which work at Layer 3, it is important to eliminate any problems that may exist at lower layers.

Students completing this module should be able to:

• Describe the differences between EIGRP and IGRP
• Describe the key concepts, technologies, and data structures of EIGRP
• Understand EIGRP convergence and the basic operation of the Diffusing Update Algorithm (DUAL)
• Perform a basic EIGRP configuration
• Configure EIGRP route summarization
• Describe the processes used by EIGRP to build and maintain routing tables
• Verify EIGRP operations
• Describe the eight-step process for general troubleshooting
• Apply a logical process to routing troubleshooting
• Troubleshoot a RIP routing process using show and debug commands
• Troubleshoot an IGRP routing process using show and debug commands
• Troubleshoot an EIGRP routing process using show and debug commands
• Troubleshoot an OSPF routing process using show and debug commands