7 Replies Latest reply: Jul 12, 2011 10:41 AM by Elvin Arias RSS

    K values


      the way i understand k values is that they are used to change the way eigrp chooses a route ie instead of using Bandwidth and delay if you turn on a k value then eigrp will also use that in its calculation's. so if you turn on k4 plus the defaults then the why eigrp works is 256* bw + delay + reliability? is this correct?

        • 1. Re: K values

          so i just found out you can change hte k values so does this mean that if you change the k values value then it also uses that in the calculation ie k4 to 100 then it would be 256 * bw + delay +100 * delay?

          • 2. Re: K values

            Cisco recommends changing delay, not bandwidth, if you have to;

            Delay is the sum of delays on a link; so add 2 delays before using it in formula

            bandwidth is the lowest value out of 2 on the link;

            • 3. Re: K values

              I would recommend NOT changing the K values at all.  If you want to tweak EIGRP metrics, you can modify the delay on an interface.  Changing bandwidth is also a possibility however if you are using QoS or monitoring software, that can throw many things out of  sync and mess with your results/plans.  Delay is a safe bet.

              • 4. Re: K values
                Scott Morris - CCDE/4xCCIE/2xJNCIE

                heheheh...  Always be careful what you wish for.   I had a client (against recommendation) who decided to change the K values to take load into account.   While it may SOUND like a good idea because routes can change based on link utilization....  


                You always have to think about the impact on your routers too!  how many routes?  How often will values change?  How much to you like your network freaking out? 


                I'd agree that you don't change it unless you need to.  As you move into the CCIE lab studies, you'll "need" to because the lab will likely say so!



                • 5. Re: K values

                  thanks guys but i was more after if i had got the thory right?

                  • 6. Re: K values
                    Sanjay Singh

                    Hi Scott,


                    Yes, if we change the any k value other than default then EIGRP metrics get changed.


                    But, Cisco recommands to not to change the default values k1=1, k2=0, k3=1, k4=0, k5=0.


                    where k1 is bandwidth, k2 is load, k3 is delay, k4 is reliability and k5 is MTU.


                    Load on a link depend on the traffic on that link and as the traffic increases/decreases, value of load changes and if you are using k2=1, then metrics also changes with traffic load.


                    Reliability of a link also varies between 0 to 255 depends on errors on link and end user device`s capabilty.


                    MTU depends on the technology standards means on fibre links MTU is different then 802.3. so if there are differrent media are used in a network then it can be a problem.


                    Rest of the two are predefined and not changes automatically.




                    • 7. Re: K values
                      Elvin Arias

                      Hello Scott_O'Brien,


                      You are right in yout thoughts. EIGRP will take reference of calculations that you globally specify with the "metric weight" command (in protocol config mode) or per route basis using route-maps and setting the routes with the metric that you will inside the route-map. Awesome stuff!