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.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s