IGRP metrics

IGRP metrics

7.3.2 This page will describe the metrics that IGRP uses.

The show ip protocols command displays parameters, filters, and network information about the routing protocols in use on the router. The algorithm used to calculate the routing metric for IGRP is shown in the graphic. It defines the value of the K1 to K5 metrics and provides information about the maximum hop count. The metric K1 represents bandwidth and the metric K3 represents delay. By default the values of the metrics K1 and K3 are set to 1, and K2, K4, and K5 are set to 0.

This composite metric is more accurate than the hop count metric that RIP uses to choose a path to a destination. The path that has the smallest metric value is the best route.

IGRP uses the following metrics:

• Bandwidth – The lowest bandwidth value in the path

• Delay – The cumulative interface delay along the path

• Reliability – The reliability on the link toward the destination as determined by the exchange of keepalives
• Load – The load on a link toward the destination based on bits per second

IGRP uses a composite metric. This metric is calculated as a function of bandwidth, delay, load, and reliability. By default, only bandwidth and delay are considered. The other parameters are considered only if enabled through configuration. Delay and bandwidth are not measured values, but are set with the delay and bandwidth interface commands. The show ip route command in the example shows the IGRP metric values in brackets. A link with a higher bandwidth will have a lower metric and a route with a lower cumulative delay will have a lower metric.

The next page will discuss the IGRP routes.