Nwtrlc [K1eWl3RPmfcl K2 BWlGftPW26W0A0H K30LYlQfl Pwm REUAffl LnrYM

where BWIGRP(min) is the minimum BWIGRP of all the outgoing interfaces along the route to the destination and DLYiGRP(sum) is the total DLYigrp of the route.

The values k1 through k5 are configurable weights; their default values are k1=k3=1 and k2=k4=k5=0. These defaults can be changed with the command:

metric weights tos k1 k2 k3 k4 k5[3]

If k5 is set to zero, the [k5/(RELIABILITY+k4)] term is not used.

Given the default values for k1 through k5, the composite metric calculation used by IGRP reduces to the default metric:

The network example in Figure 6.7 shows the bandwidths and delays configured on each interface and a forwarding database from one of the routers with the derived IGRP metrics.[4]

[4] Also notice the administrative distance, which is 100 for IGRP.

Figure 6.7. By default, the total delay is added to the minimum bandwidth to derive the IGRP metric.

Figure 6.7. By default, the total delay is added to the minimum bandwidth to derive the IGRP metric.

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The routing table itself shows only the derived metric, but the actual variables recorded by IGRP for each route can be seen by using the command show ip route address, as in Figure 6.8. Here the minimum bandwidth on the route from Casablanca to subnet 172.20.40.0/24 is 512K, at Quebec. The total delay of the route is (1000 + 20000 + 20000 + 5000) = 46000 microseconds.

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