EIGRP: Manual Influence on Path Selection

Based on the components of classic/wide metrics, the only two components that can be manually influenced are Bandwidth/Throughput and Delay/Latency.

It is explicitly outlined in draft-savage-eigrp that manipulating the bandwidth metric for best path selection is discouraged for the following reasons:

  • Changing the bandwidth can have an impact beyond affecting the EIGRP metrics, such as QoS since it also references the bandwidth of the interface.
  • EIGRP defaults to throttle 50 percent of the configured bandwidth, lowering the bandwidth can cause problems like starving EIGRP neighbors from getting packets, on the flip side configuring bandwidth to high can lead to EIGRP consuming more bandwidth than physically able leading to packet drops.

Changing delay does not impact any other protocol nor does it cause EIGRP to throttle back, and since it influences the sum of all delays on that specific path it directly affects path selection.


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