Enhanced Interior Gateway Routing Protocol
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Therefore, it is possible for EIGRP to have nine active databases when all
three protocols are configured on the router.
As stated above, the metrics used by EIGRP are the same as those used by
IGRP. As with IGRP, metrics decide how routes are selected. The higher the
metric associated with a route, the less desirable the route is. The overall metric
assigned to a route is created by the Bellman-Ford algorithm, using the
following equation:
metric = [K1
Ч Bw + (K2 Ч Bw) / (256 Load) + K3 Ч Delay] Ч [K5 /
(Rel + K4)]
By default: K1 = 1, K2 = 0, K3 = 1, K4 = 0, K5 = 0.
Delay is the sum of all the delays of the links along the paths.
Delay = [Delay in 10s of microseconds]
Ч 256.
BW is the lowest bandwidth of the links along the paths.
BW = [10000000 / (bandwidth in Kbps)]
Ч 256.
By default, metric = bandwidth + delay.
Just as with IGRP, you can set the metrics manually from within the Con-
figuration mode. We'll provide the details on how to change metrics after we
discuss how EIGRP is configured.
Configuring EIGRP
Although EIGRP can be configured for IP, IPX, and AppleTalk, as a Cisco
Certified Network Professional, you should focus on the configuration of IP.
An autonomous system must be defined for each EIGRP session on a router.
To start an EIGRP session on a router, use the router eigrp command fol-
lowed by the autonomous system number of your network. You must then
enter the network numbers connected to the router using the network com-
mand followed by the network number. The network mask is optional for
network statements entered on the Cisco IOS 12.0 or later.
Let's look at an example of enabling EIGRP on a router connected to two
networks with the network numbers 10.0.0.0 and 172.16.0.0:
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router#router eigrp 20
Router(config-router)#network 172.16.0.0
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