EIGRP offers the following features:
● Fast convergence—The DUAL algorithm allows routing information to converge as quickly as any currently available routing protocol.
● Partial updates—EIGRP sends incremental updates when the state of a destination changes, instead of sending the entire contents of the routing table. This feature minimizes the bandwidth required for EIGRP packets.
● Less CPU usage than IGRP—This occurs because full update packets need not be processed each time they are received.
● Neighbor discovery mechanism—This is a simple hello mechanism used to learn about neighboring routers. It is protocol-independent. Security requirements do not allow dynamic learning of neighbors. BFD should be used to detect loss of a neighbor.
● Variable-length subnet masks (VLSMs).
● Arbitrary route summarization.
● Scaling—EIGRP scales to large networks.
EIGRP uses split horizon or advertises a route as unreachable when:
● two routers are in startup mode (exchanging topology tables for the first time)
● advertising a topology table change
● sending a query
Poison reverse is a loop avoidance mechanism that states that once you learn of a route through an interface, advertise it as unreachable back through that same interface.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3007-3011). . Kindle Edition.