7 Replies Latest reply: May 28, 2014 2:40 PM by alib_15 RSS

    EIGRP METRIC.

    Krishna

      EIGRP.jpg

       

      What will be the EIGRP metric that the Router B advertises to Router A for the networks 1.0.0.0( Loop back on Router B) and 10.0.0.0(B-C Faster ethernet connection)

       

      Krishna

        • 1. Re: EIGRP METRIC.
          Vijay Swaminathan

          HI Krishna,

           

          The formulae for calculating EIGRP metric is:

           

          Metric = 256*((K1*Bw) + (K2*Bw)/(256-Load) + (K3*Delay)*(K5/(Reliability + K4)))

           

          k1=bandwidth

          k2=load

          k3=delay

          k4=reliability

          k5=MTU

           

          usuallly only Bandwidth and Delay are considered for Bandwidth calculation (by default) . so K1 = 1 and K3 = 1 and rest all are Zero. (although you can change these metric weights (k- values))

           

          applying that on the formula.

           

          the Metric would be

           

          256 *( (k1 * BW) + (K3 * Delay))

           

          BW is Minimum Bandwidth in kpbs and delay is cummulative delay in tens of microseconds.

           

          Apply BW and Delay of that interface in the above said formula and you should be able to calculate the metric.

           

          Hope this helps

           

          -Vijay

          • 2. Re: EIGRP METRIC.
            Martin

            Metric = 256 * ((10000000 / slowest bandwidth) + cumulative delay)

             

            other K values are usually skipped; not recommended to be used

             

            there is a post with few links to online eigrp metric calc.

             

            and Brian has one in his docs https://learningnetwork.cisco.com/docs/DOC-8176

            • 3. Re: EIGRP METRIC.
              Krishna

              What are the  bandwidth and delay in this case?

               

              Krishna

              • 4. Re: EIGRP METRIC.
                Martin

                you take the lowest bandwidth of the link, so RB take Band. between RC and RB and sum of delays; figure metric out and it sends metric out to RA.

                 

                show interface fa x/y will give you info

                 

                Loopbacks are special case. there is something wierd with those.

                • 5. Re: EIGRP METRIC.
                  Brian

                  Just to expound on the other posts. On Router B, do a "sh ip eigrp top 1.0.0.0 <mask>" and "sh ip eigrp top 10.0.0.0 <mask>".  Here is an example, I have loopback 10.2.2.0/24 on R2 and the R2-R3 connection is 10.1.2.0/30.  The metric as seen by R2 which would be the RD metric R2 sends to R3 is

                   

                  R2#sh ip eigrp top 10.2.2.0 255.255.255.0
                  IP-EIGRP (AS 100): Topology entry for 10.2.2.0/24
                    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 128256
                    Routing Descriptor Blocks:
                    0.0.0.0 (Loopback10), from Connected, Send flag is 0x0
                        Composite metric is (128256/0), Route is Internal
                        Vector metric:
                          Minimum bandwidth is 8000000 Kbit
                          Total delay is 5000 microseconds
                          Reliability is 255/255
                          Load is 1/255
                          Minimum MTU is 1500
                          Hop count is 0
                  R2#sh ip eigrp top 10.1.2.0 255.255.255.252
                  IP-EIGRP (AS 100): Topology entry for 10.1.2.0/30
                    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2169856
                    Routing Descriptor Blocks:
                    0.0.0.0 (Serial0/0), from Connected, Send flag is 0x0
                        Composite metric is (2169856/0), Route is Internal
                        Vector metric:
                          Minimum bandwidth is 1544 Kbit
                          Total delay is 20000 microseconds
                          Reliability is 255/255
                          Load is 1/255
                          Minimum MTU is 1500
                          Hop count is 0
                  R2#


                  Below is the metric (FD) as seen by R3:

                   

                  R3#sh ip eigrp top 10.2.2.0 255.255.255.0
                  IP-EIGRP (AS 100): Topology entry for 10.2.2.0/24
                    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2297856
                    Routing Descriptor Blocks:
                    10.1.2.2 (Serial0/0), from 10.1.2.2, Send flag is 0x0
                        Composite metric is (2297856/128256), Route is Internal
                        Vector metric:
                          Minimum bandwidth is 1544 Kbit
                          Total delay is 25000 microseconds
                          Reliability is 255/255
                          Load is 1/255
                          Minimum MTU is 1500
                          Hop count is 1
                  R3#sh ip eigrp top 10.1.2.0 255.255.255.252
                  IP-EIGRP (AS 100): Topology entry for 10.1.2.0/30
                    State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2169856
                    Routing Descriptor Blocks:
                    0.0.0.0 (Serial0/0), from Connected, Send flag is 0x0
                        Composite metric is (2169856/0), Route is Internal
                        Vector metric:
                          Minimum bandwidth is 1544 Kbit
                          Total delay is 20000 microseconds
                          Reliability is 255/255
                          Load is 1/255
                          Minimum MTU is 1500
                          Hop count is 0
                  R3#

                   

                  You will notice that the link between them really does not have a metric that is advertised as it is directly connected to each router.  Hence the RED ZERO in the output above.  In addition you can see the values that EIGRP used for bandwidth and delay in the metric calculation.


                  Hope this helps.

                   

                  Brian

                   

                  • 6. Re: EIGRP METRIC.
                    Martin

                    WoW, Brian likes EIGRP and GNS3. Very helpful, thanks

                    • 7. Re: EIGRP METRIC.
                      alib_15

                      Good discussion of EIGRP metric calculation

                      but K5 ≠ mtu