Cisco ASA 5505 Configuration Manual page 421

Configuring EIGRP
This chapter describes how to configure the adaptive security appliance to route data, perform
authentication, and redistribute routing information, using the Enhanced Interior Gateway Routing
Protocol (EIGRP).
The chapter includes the following sections:
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Overview
EIGRP is an enhanced version of IGRP developed by Cisco. Unlike IGRP and RIP, EIGRP does not send
out periodic route updates. EIGRP updates are sent out only when the network topology changes. Key
capabilities that distinguish EIGRP from other routing protocols include fast convergence, support for
variable-length subnet mask, support for partial updates, and support for multiple network layer
protocols.
A router running EIGRP stores all the neighbor routing tables so that it can quickly adapt to alternate
routes. If no appropriate route exists, EIGRP queries its neighbors to discover an alternate route. These
queries propagate until an alternate route is found. Its support for variable-length subnet masks permits
routes to be automatically summarized on a network number boundary. In addition, EIGRP can be
configured to summarize on any bit boundary at any interface. EIGRP does not make periodic updates.
Instead, it sends partial updates only when the metric for a route changes. Propagation of partial updates
is automatically bounded so that only those routers that need the information are updated. As a result of
these two capabilities, EIGRP consumes significantly less bandwidth than IGRP.
Neighbor discovery is the process that the adaptive security appliance uses to dynamically learn of other
routers on directly attached networks. EIGRP routers send out multicast hello packets to announce their
presence on the network. When the adaptive security appliance receives a hello packet from a new
OL-20339-01
Overview, page 23-1
Licensing Requirements for EIGRP, page 23-2
Guidelines and Limitations, page 23-2
Task List to Configure an EIGRP Process, page 23-3
Enabling EIGRP, page 23-4
Customizing EIGRP, page 23-6
Monitoring EIGRP, page 23-18
Configuration Example for EIGRP, page 23-18
Feature History for EIGRP, page 23-20
C H A P T E R
Cisco ASA 5500 Series Configuration Guide using ASDM
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