What is EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is a classless routing protocol that directly interfaces to Internet Protocol (IP) as protocol 88.
IPX Routing Protocols
AppleTalk Routing Protocol
AppleTalk Routing Protocol
AppleTalk Routing Protocol )
IPX Routing Protocols
EIGRP supports:
* Rapid convergence
* Reduced bandwidth usage
* Multiple network-layer protocols
AppleTalk Routing Protocol )
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Cisco CCIE Prep v1.0—MoCule6-37
EIGRP uses the multicast address of 224.0.0.10 for 'hellos' and routing updates instead of an all hosts broadcast like Routing Information Protocol (RIP) uses. EIGRP also employs a system of hello and hold timers to maintain neighbors. Aside from the initial routing update, partial routing updates are sent only when network topology changes occur. The updates are also "bounded", which means updates are sent only to pertinent routers. Like IGRP, EIGRP uses a composite metric to calculate the best path to a destination. The sections that follow take a closer look at how EIGRP makes use of metrics, neighbors, reliable transport, and Diffusing Update Algorithm (DUAL) in its operation. Some EIGRP features are as follows:
■ Support for Variable Length Subnet Mask (VLSM): EIGRP is a classless routing protocol, and carries the subnet mask of the route in its update.
■ Rapid convergence: By using the concept of feasible successors, defined by DUAL, EIGRP is able to pre-select the next best path to a destination. This allows for very fast convergence upon a link failure.
■ Low Central Processing Unit (CPU) utilization: Under normal operation only 'hellos' and partial updates are sent across a link. Routing updates are not flooded and processed only periodically.
■ Incremental updates: EIGRP does not send full routing updates, it only sends information about changed routes.
■ Scalable: Through the use of VLSM and a complex composite metric, EIGRP networks can scale dramatically in size.
■ Easy configuration: EIGRP supports hierarchical network design, but it does not require the strict configuration guidelines, such as the ones needed for Open Shortest Path First (OSPF).
■ Automatic route summarization: EIGRP will perform automatic summarization on major bit boundaries.
■ Message Digest Version 5 (MD5) route authentication: (as of Cisco Internetwork Operating System (IOS) Software Release 11.3) EIGRP can be configured to perform MD5 password authentication on route updates.
Continue reading here: Basic Eigrp Configuration
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