K values

[vishalpatil86]

Hi all,

I have a question on K values used in eigrp routing...

It is said that to form a neighborship, k values must be the same; Is it necessary that K values weight must be same??

eigrp by default uses k1 and k3 i.e. bandwidth and delay with weight 1..

if the weights are differnet then do they form a neighborship??                  

[Reza Sharifi]

Hi,

You have to use the metric weight command to change the K values:

here are the values:

Router(config-router)# metric weights tos k1 k2 k3 k4 k5

Adjusts the EIGRP metric or K value. EIGRP uses the following formula to determine the total metric to the network: metric = [K1*bandwidth + (K2*bandwidth)/(256 - load) + K3*delay] * [K5/(reliability + K4)]

Mismatched K Values

Mismatched K values (EIGRP metrics) can prevent neighbor relationships  from being established and can negatively impact network convergence.  The following example explains this behavior between 2 EIGRP peers  (ROUTER-A and ROUTER-B).

The following error message is displayed in the console of ROUTER-B because the K values are mismatched:

*Apr 26 13:48:41.811: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 10.1.1.1 (Ethernet0/0) is down: K-value mismatch

There are two scenarios where this error message can be displayed:

•The  two routers are connected on the same link and configured to establish a  neighbor relationship. However, each router is configured with  different K values.

The following configuration is applied to ROUTER-A. The K values are changed with the metric weights command. A value of 2 is entered for the k1 argument to adjust the bandwidth calculation. The value of 1 is entered for the k3 argument to adjust the delay calculation.

hostname ROUTER-A!

interface serial 0 

 ip address 10.1.1.1 255.255.255.0 

 exit

router eigrp 100 

 network 10.1.1.0 0.0.0.255 

 metric weights 0 2 0 1 0 0

The following configuration is applied to ROUTER-B. However, the metric weights command is not applied and the default K values are used. The default K values are 1, 0, 1, 0, and 0.

hostname ROUTER-B!

interface serial 0

 ip address 10.1.1.2 255.255.255.0!

 exit

router eigrp 100 

 network 10.1.1.0 0.0.0.255

The bandwidth calculation is set to 2 on ROUTER-A and set to 1 (by  default) on ROUTER-B. This configuration prevents these peers from  forming a neighbor relationship.

•The  K-value mismatch error message can also be displayed if one of the two  peers has transmitted a "goodbye" message, and the receiving router does  not support this message. In this case, the receiving router will  interpret this message as a K-value mismatch.

link for reference:

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfeigrp.html

HTH

[rizwanr74]

Hi Vishal,

"if the weights are differnet then do they form a neighborship??" Yes. 

"It is said that to form a neighborship, k values must be the same; Is it necessary that K values weight must be same??" no.

Bandwidth (K1) and delay(K3) can be change, will not affect neighbor relationship on interface level.

Reliablity (K4), Load (K2), and MTU (K5) will cause problem in neighbor relationship.

Hope this answers your question.

thanks

Rizwan Rafeek

Message was edited by: Rizwan Mohamed

[John Blakley · Accepted solution]

Vishal,

You can change the K values, but they have to match between neighbors for a neighborship to come up. If you change it on one, then you'll have to change them on all. By default, BW and Delay are the 2 K values that are used in the calculation of your metric: K1=1 K2=0 K3=1 K4=0 K5=0. If you change any of these from their defaults, you'll have to change all of your routers. If you have mismatched K values, you'll get an error like below:

*Mar  1 00:04:06.883: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 172.1.12.2 (FastEthernet0/0) is down: K-value mismatch

"show ip protocols" shows us the configured K value:

On Router I just changed:

Routing Protocol is "eigrp 100"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  Default networks flagged in outgoing updates

  Default networks accepted from incoming updates

  EIGRP metric weight K1=0, K2=0, K3=0, K4=0, K5=1

On neighboring router (the default is K1=1, K2=0, K3=1, K4=0, K5=0

Routing Protocol is "eigrp 100"

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  Default networks flagged in outgoing updates

  Default networks accepted from incoming updates

  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0

You won't get a neighborship if these values don't match.

HTH,

John

[vishalpatil86]

thanks to all guys...