Limiting EIGRPs Bandwidth Utilization

Limiting EIGRP s Bandwidth Utilization

Problem

You want to limit the fraction of an interface's bandwidth available to EIGRP for routing updates.

Solution

To modify the amount of bandwidth percentage available to EIGRP, use the ip bandwidth-percent configuration command:

Router1#configure terminal 
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#interface Serial0.1
Router1(config-subif)#ip bandwidth-percent eigrp 55 40
Router1(config-subif)#exit
Router1(config)#end
Router1#

 

Discussion

The example above shows how to restrict EIGRP to use at most 40 percent of the available capacity of this link. By default, EIGRP limits its own bandwidth utilization to ensure that it never takes more than 50 percent of a link's capacity. However, this default isn't always appropriate. Sometimes you need to reduce this fraction to reduce overall congestion. And sometimes the total bandwidth value specified on an interface is not accurate.

For example, in Recipe 7.6, we discussed how to change what the router thinks the interface's bandwidth is. If this value is significantly lower than the real physical bandwidth of the interface, you might want to increase the fraction that EIGRP can use. This can help to improve network convergence times when EIGRP needs to suddenly exchange a large amount of routing information.

In the following example, we have manually reduced bandwidth value on this 128 kbps interface to 32 kbps to affect the EIGRP metric. Since this is much less than the true value, we have then increased the fraction that EIGRP can use to 200 percent, bringing it up to a maximum of 56 kbps, which would be the default for a real 128 kbps circuit:

Router1#configure terminal 
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#interface Serial0.1 
Router1(config-subif)#bandwidth 32
Router1(config-subif)#ip bandwidth-percent eigrp 55 200
Router1(config-subif)#exit
Router1(config)#end
Router1#

 

See Also

Recipe 7.6