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16940 Views 6 Replies Latest reply: Nov 28, 2011 11:00 PM by Martin RSS

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EIGRP METRIC.

Nov 28, 2011 8:39 PM

Krishna 712 posts since
Aug 24, 2011

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

  • Vijay Swaminathan 491 posts since
    Aug 29, 2008
    Currently Being Moderated
    1. Nov 28, 2011 8:50 PM (in response to Krishna)
    Re: EIGRP METRIC.

    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

  • Martin 13,075 posts since
    Jan 16, 2009
    Currently Being Moderated
    2. Nov 28, 2011 8:59 PM (in response to Krishna)
    Re: EIGRP METRIC.

    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

  • Martin 13,075 posts since
    Jan 16, 2009
    Currently Being Moderated
    4. Nov 28, 2011 9:05 PM (in response to Krishna)
    Re: EIGRP METRIC.

    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.

  • Brian 2,971 posts since
    Aug 17, 2009
    Currently Being Moderated
    5. Nov 28, 2011 9:07 PM (in response to Krishna)
    Re: EIGRP METRIC.

    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

  • Martin 13,075 posts since
    Jan 16, 2009
    Currently Being Moderated
    6. Nov 28, 2011 11:00 PM (in response to Brian)
    Re: EIGRP METRIC.

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

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