EIGRP load and reliability

[kamlesh.sharma]

How EIGRP calculates load and reliability.

how can i reset the values to make my high bandwidth path to be best route again.

is this related to 5 min input and output calculation.

In EIGRP RTS/SRTT values are propritory and on this load and reliability is depend i think

please help

thanks in advance

[amit-singh]

Hi Kamlesh,

By default, EIGRP doesnot take Load and reliability into consideration. As K1=1,K2=0,K3=1,K4=0,K5=0.Its takes bandwidth and delay into account for calculating the metric. If you want EIGRP to take all the 5 parameters into account, then either it can be configured to use default values under the interfaces or the vlaues that you want.

HTH,

-amit singh

[ruwhite · Accepted solution]

"How EIGRP calculates load and reliability?"

EIGRP doesn't calculate load and reliability, it takes them from the interface counters, as calculated by interface code. Generally, load is based on the amount of bandwidth available (based on the configured bandwidth), converted to a number between 0 and 255 (so 255 is 100% load, while 0 is 0% load). Reliability is generally based on packets dropped, or errors, depending on the interface type, and is also adjusted to be between 0 and 255.

Note that while these numbers are dynamic, EIGRP doesn't read them from the interface dynamically. In other words, when the EIGRP neighbor relationship first comes up, the reliability and load are read from the interface, and after that, they remain constant, from EIGRP's perspective, until the neighbor relationship on the interface is cleared.

HTH.

:-)

Russ.W

[Richard Burts]

Russ makes a good point that the load and reliability are read when the neighbor relationship is formed and do not change dynamically. I believe that another aspect to point out is that (at least by default) while EIGRP gets the values and includes the values in advertisements, EIGRP does not use these values in calculatint the route metric. Based on the default K values EIGRP uses the bandwidth and delay but not the reliability or load or MTU.

HTH

Rick

[egbevanwatson]

I am still confused about why Load and Reliability are not used by default in the metrics calculation. Below is my understanding, and I'm wondering if I am correct.

According to my understanding, when the EIGRP neighbor relationship first comes up, EIGRP reads Load and Reliability values dynamically from the interface and this values aren’t static.

After the initial reading, EIGRP continues to monitor the interface and dynamically updates Load and Reliability based on changes in network conditions, such as variations in traffic load or link stability. The Load value reflects the current traffic load on the interface, and the Reliability value reflects the current stability of the link Correct?  As conditions change (e.g., increased or decreased traffic, changes in link stability), EIGRP dynamically adjusts these metrics.

This is in the case where these attributes are enabled for metric calculations. If these values used, there will be a recalculation of the metrics anytime these values change in load and reliability since they are dynamic.

While Load and Reliability are updated dynamically, changes in these metrics alone do not trigger immediate EIGRP updates. EIGRP updates are typically triggered by changes in the network topology or significant events rather than incremental changes in Load or Reliability.

In summary, EIGRP actively and dynamically reads Load and Reliability from the interface, adjusting the metrics in real-time to reflect the current state of the network (if used in the metrics calculation). The values are not static and can change without the need to clear the neighbor relationship.

Please can you correct me where I went wrong? Thanks in advance.