EIGRP K values

EIGRP uses a composite metric and K-values to calculate the preferred path to a destination.

EIGRP K Values Types –

Below table details on the 5 K-value types and corresponding default Cisco value on devices while calculating EIGRP metric to a destination.

Related – EIGRP Interview Questions

EIGRP k values metric calculation –

The formula for the computation of EIGRP metric is –

It’s important to understand where to find the EIGRP k values in the Cisco network devices. The command “show interfaces (interface name)” will provide the detail of all the K-values i.e. Bandwidth, Load, delay, Reliability and MTU.

Another important show command to show the K values presently used the cisco device (default values) –

“Show ip protocols”

Now, let’s understand from an example scenario which will illustrate how EIGRP composite metric is calculated for Network 1.1.1.0/24 (Loopback 0 of Router R1). Routers R1, R2 and R3 are all connected in series with Loopback 0 of R1 (IP =1.1.1.1/24) advertised in EIGRP domain. We are considering default K-values calculation mechanism i.e. K1 = K3 = 1 and K2=K4=K5 = 0.

Related Bl0g – Configuring EIGRP Stub FEATURE

Computation formula –

On Router R1, since Loopback 0 (1.1.1.0/24) is directly connected, hence the metric comes out to be 0. Now let’s see how R2 interprets metric for reaching Loopback 0 of R1 –

As above, the minimum bandwidth will be decided from one of the 2 i.e.  (1) Loopback 0 of R1 (2) Interface fa0/0 of R2. For computation, bandwidth of 10000 Kbps of R2 interface Fa0/0 will be used since it’s the minimum of the 2.

For Delay calculation, sum of both the (1) Loopback 0 of R1 and (2) Interface Fa0/0 of R2 will be taken. Hence total Delay (in microsec ) comes out to be 5000 + 1000 = 6000 Microseconds.

The final computation of metric for R2 to reach Loopback 0 of R1 comes to be 49600.Now let’s understand how R3 computes the Metric to reach Loopback 0 of R1.

As above, the minimum bandwidth calculation will be taken from one the 3 interface bandwidths (1) Loopback 0 of R1 (2)Interface Fa0/0 of R2 (3) Interface Fa0/1 of R3

Since the minimal bandwidth is 10000 Kbps on Fa0/0 of R2 and Fa0/1 of R3, the same will be used in computation as shown in above diagram.

For Delay calculation, again sum of following interfaces will be considered – (1) Loopback 0 of R1 and (2) Interface Fa0/0 of R2 (3) Interface Fa0/1 of R3. Hence total Delay (in microsec) comes out to be 5000 + 1000 + 1000= 7000 Microseconds.

Now we have clear understanding of EIGRP composite metric is calculated by K values. In the above case the default values of K1 and K3 were used while calculating the composite metric for the destination.

Continue Reading:

EIGRP Preferred Path Manipulation

EIGRP Default Network Route

ABOUT THE AUTHOR

Rashmi Bhardwaj

I am here to share my knowledge and experience in the field of networking with the goal being – “The more you share, the more you learn.”

I am a biotechnologist by qualification and a Network Enthusiast by interest. I developed interest in networking being in the company of a passionate Network Professional, my husband.

I am a strong believer of the fact that “learning is a constant process of discovering yourself.”
– Rashmi Bhardwaj (Author/Editor)