I am in a class which conforms to the material in the Cisco Companion Guides, and I am currently using the Scaling Networks textbook.

In it, the book explains how to adjust the percentage of interface bandwidth the EIGRP process is allowed to use, and that the default is 50%.

The only reason my teacher can give as to why this limit would be reached is when EIGRP is implemented on incredibly slow links.

Is this a scenario one would ever expect to see?

Are there any other real-world scenarios in which this limit could be reached?

  • The title suggests that you would like to know when it would EIGRP would exceed the limit, but the body of the question seems to suggest you would like to know when it would reach the limit. Those are two very different questions.
    – Ron Maupin
    Commented Mar 3, 2016 at 4:37
  • @RonMaupin Would it be more accurate if the title said 'approach 50%', or 'attempt to use more than 50%', instead of 'use more than 50%'? I had thought reaching and exceeding the limit were essentially synonymous. Commented Mar 3, 2016 at 4:45
  • See my answer...
    – Ron Maupin
    Commented Mar 3, 2016 at 4:55

1 Answer 1


By default, EIGRP will not use more than 50% the bandwidth configured on the interface. It could use more than 50% of the actual interface bandwidth if the bandwidth command is greater than actual the interface bandwidth.

EIGRP could use up to the default 50% configured interface bandwidth if the interface is relatively slow slow, or the configured interface bandwidth is lower than the actual interface bandwidth.

Depending on the interface speed, if the configured interface bandwidth accurately reflects the actual interface bandwidth, the EIGRP bandwidth could reach the default 50% if there are a lot of network changes which require many updates, such as flapping links, but it would need to be an extreme circumstance in modern networks.

This was important in the past with slow WAN links, but the reality is that EIGRP uses a relatively small amount of the bandwidth available on modern network interfaces. It's probably something you won't need to deal with outside lab scenarios or exams.

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