Cisco Systems 78-11741-02 manual Mismatched K Values, IPC-261

Configuring EIGRP

EIGRP Configuration Task List

To adjust the EIGRP metric weights, use the following command in router configuration mode:

Command	Purpose
Router(config-router)# metric weights tos k1 k2 k3 k4 k5	Adjusts the EIGRP metric or K value. EIGRP uses the
	following formula to determine the total metric to the
	network:
	metric = [K1*bandwidth + (K2*bandwidth)/(256 - load)
	+ K3*delay] * [K5/(reliability + K4)]

By default, the EIGRP composite metric is a 32-bit quantity that is a sum of the segment delays and the lowest segment bandwidth (scaled and inverted) for a given route. For a network of homogeneous media, this metric reduces to a hop count. For a network of mixed media (FDDI, Ethernet, and serial lines running from 9600 bits per second to T1 rates), the route with the lowest metric reflects the most desirable path to a destination.

Mismatched K Values

Mismatched K values (EIGRP metrics) can prevent neighbor relationships from being established and can negatively impact network convergence. The following example explains this behavior between 2 EIGRP peers (ROUTER-A and ROUTER-B).

The following error message is displayed in the console of ROUTER-B because the K values are mismatched:

*Apr 26 13:48:41.811: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.1.1.1 (Ethernet0/0) is

down: K-value mismatch

There are two scenarios where this error message can be displayed:

•The two routers are connected on the same link and configured to establish a neighbor relationship. However, each router is configured with different K values.

The following configuration is applied to ROUTER-A. The K values are changed with the metric weights command. A value of 2 is entered for the k1 argument to adjust the bandwidth calculation. The value of 1 is entered for the k3 argument to adjust the delay calculation.

hostname ROUTER-A! interface serial 0

ip address 10.1.1.1 255.255.255.0 exit

router eigrp 100

network 10.1.1.0 0.0.0.255 metric weights 0 2 0 1 0 0

The following configuration is applied to ROUTER-B. However, the metric weights command is not applied and the default K values are used. The default K values are 1, 0, 1, 0, and 0.

hostname ROUTER-B! interface serial 0

ip address 10.1.1.2 255.255.255.0! exit

router eigrp 100

network 10.1.1.0 0.0.0.255

The bandwidth calculation is set to 2 on ROUTER-A and set to 1 (by default) on ROUTER-B. This configuration prevents these peers from forming a neighbor relationship.

Cisco IOS IP Configuration Guide

IPC-261