EIGRP IP bandwidth-percent example

When configuring the IP Bandwidth-percent parameter in EIGRP, how do you determine what percent you should set this parameter to? It depends upon:

  • the bandwidth of the link
  • the size of the EIGRP topology table

Taking the following into account will give a better understanding of the kinds of bandwidths that EIGRP packet exchanges require:

  • An EIGRP update with a single prefix is about 96 bytes including all headers.
  • Hello packets can be anywhere from 60 to over 80 bytes in length.
  • Hello packets are exchanged every 5 seconds on links with bandwidths greater than a T1 (1.544 Mbps) and every 60 seconds on slower links.
  • Updates are sent only when the topology changes

This features should be used in the event that you are advertising hundreds or thousands of prefixes using EIGRP over links that are smaller than T1s. Otherwise it is unnecessary in most cases.