The routing protocol EIGRP (Extended Internal Gateway Routing Protocol), and Cisco proprietary enhanced version of IGRP is a hybrid protocol that has characteristics of both distance vector and link state and is usually used in medium to large networks.
EIGRP Features
- Default Metrics: Bandwidth + Delay.
- It has an administrative distance of 90 domestic and 170 foreign.
- Supports up to 255 dives (100 by default).
- Using the DUAL algorithm for upgrades and fast convergence.
- Partial updates triggered by events.
- Supports IP, IPv6, IPX and AppleTalk.
- Supports classless routing, VLSM arbitrary and summary routes.
EIGRP Table:
- Neighborhood Table: This table keeps EIGRP routes to neighboring routers (directly connected).
- Topology Table: This table keeps EIGRP routes the destinies of their neighboring routers.
- Routing Table: This table with information from the “Table of Topology” EIGRP chooses the best route to each destination.
EIGRP Operation:
The adjacent routers (neighbors) in the same autonomous system exchange their neighbor table, assemble the “Table of Topology” and produce Routing Table with the best routes to destinations (successor). In case of failure EIGRP has the ability to use alternative routes (feasible successor) lookup to a destination.
Syntax EIGRP configuration
router (config) # router eigrp 240
router (config-router) # network network-number
router (config-if) # bandwidth kilobits
router (config-router) # eigrp log-neighbor-changes
router eigrp 240 specified as EIGRP routing protocol for autonomous system 240, this value varies from 1 to 65535
specific network of networks directly connected to the router to be advertised by EIGRP
bandwidth the routing process use the bandwidth command to calculate the metric and should set the command to match the line speed of the interface.
log-neighbor-changes enables logging of neighbor adjacency changes to monitor routing system stability and to help detect problems.
In current versions of IOS EIGRP network command adds the wildcard for the protocol that allows the identification of subnets,
router (config) # router eigrp 240
router (config-router) # network 192.168.16.0 0.0.0.255
Some commands to control verification and EIGRP are:
show ip route
Displays the routing table
show ip protocols
Displays protocol parameters
show ip eigrp Neighbors
Display information on EIGRP neighbors
show ip eigrp topology
Displays the EIGRP topology table
debug ip eigrp
Displays information about packages
The basic configuration of EIGRP is fairly easy; however, a more advanced configuration requires a bit more details to consider.