EIGRP K Values Configuration

(Rene Molenaar) #1

This topic is to discuss the following lesson:

(William K) #2

Is there any reason in a real world deployment you might not want to disable BW? It seems more deterministic to use just BW.

(Maher H) #3

Hi William,

As Rene has mentioned in the lesson, Cisco by default has Bandwidth and delay enabled while load and reliability are disabled as they change dynamically and Cisco recommended us to not enable them.

So in other term, Cisco wanted to say keep BW and delay only active. In the real world, I don’t see any reason to disable BW & delay. In case you want to disable any of them then it is better to disable the delay and keep the bandwidth enabled because the delay is calculated based on the sum of delays in the path as per the below formula’s

Metric = bandwidth (slowest link) + delay (sum of delays)

Here a good lesson explaining EIGRP K Values for more information.

Hope I could answer your question

(Stuart G) #4

Hi William,
The calculation is sum of all the delays and the lowest bandwidth.
So if you only enable the bandwidth then essentially the path length is not taken into consideration.
Usually you would prefer a shortest path if all the bandwidths are the same.


(Stefanio L) #5

Hi, Rene.

I was reading and researching on Google about the K6, and they say it represents jittler and energy. Jittler makes sense, but energy can’t understand. Are you going to use electricity as a metric? LOL

Would you know clearly how to explain the real need of K6 and how the metric is calculated?

(Rene Molenaar) #6

Hi Stefanio,

As weird as it sounds, that’s exactly what they intend with energy yes :smile:

Here’s an excerpt from RFC 7868:

https://tools.ietf.org/html/rfc7868#page-41 Energy

Use of Energy-based Path Selection results in paths with the lowest
energy usage being selected in a loop-free and deterministic manner.
The amount of energy used is accumulative and has results in a higher
aggregate metric than those having lower energy.

Presently, EIGRP does not report energy usage, and as such the
default value will be zero (0).

On the Cisco site, you can find this:

likewise energy would be expressed in power per kilobytes per second of usage

So the idea is to select an interface, based on how much power it consumes.

You can find the wide metrics formula (that includes K6) here:

Hope this helps!


(AZM U) #7

I am going to use the below topology as a reference for my question.

I am trying to manipulate EIGRP path by changing the interface delay on ROUTER-1.
By default, this is how everything looks like.

Then I increased the interface delay and now the prefix is showing up as
FD is Infinity in the EIGRP topology table and the prefix is not in the routing table anymore. Additionally, I am not running any other routing protocol and don’t have any static route either. Please shed some light on it.

Thank you so much in advance.

Best Regards,
Azm Uddin