Interior Gateway Routing Protocol (IGRP) adds together weighted values of different characteristics of the link to the network in question in order to calculate a metric. The link characteristics from which IGRP calculates a composite metric are bandwidth, delay, load, reliability, and maximum transmission unit (MTU). By default, IGRP chooses a route based on bandwidth and delay.
Network Diagram
The diagram for the given scenario is provided here:
Here is the formula used to calculate the composite metric for IGRP:
Metric = [K1 * Bandwidth + (K2 * Bandwidth)/(256-load) + K3*Delay] * [K5/(reliability + K4)]
The default constant values are K1 = K3 = 1 and K2 = K4 = K5 = 0.
If K5 = 0, the [K5/(reliability + K4)] term is not used. So, given the default values for K1 through K5, the composite metric calculation used by IGRP reduces to Metric = Bandwidth + Delay.
The K values in these formulas are constants that you are able to define with the router configuration command, metric weights tos k1 k2 k3 k4 k5 .
Note: Cisco strongly suggests that you do not change the default K parameters.
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