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Forum Replies

  1. Hello Rene,

    this was a really good post! One statement that I personally dont liked:

    “ou don’t want your EIGRP routers calculating 24/7 and sending updates to each other just because the load or reliability of an interface has changed. We want routing protocols to be nice and quiet and only base their routing decisions on static values like bandwidth and delay.”

    I think everyone would love to have a routing protocol that dynamically adapts to the network state but the processing overhead for the routers in your network would be a nightmare.

    Thank you for this post.


  2. system says:

    EIGRP Metric = 256*[(K1 x BW) + ((K2 x BW)/(256-Load)) + (K3 x Delay) x ((K5/(Reliability + K4))]

    Known as EIGRP “Distance” on the exam.

  3. Hi Rene,

    I understood that if the delay was in ten of microsecond we only sum the delays of the links and if the delay was in microsecond we need to divide the sum on 10 and put the value to formula, and about BW I do not understand why we multiply by 10^7 when I read in Wiki I understand the we do that to make the formula weighted and make measuring units harmonized but I do not understand how ? I mean why 10^7 ? from where this number come ?

  4. Hi Diego,

    That is correct, I just fixed it. Thanks for reporting!


  5. I’m about 2 years too late but I’d like to take a crack at this for future reference. The reason 10^7 is used is because 10^7=10,000,000 kbps which is the same things as 10Gbps. When this formula was developed into what it is today, 10gbps was insanely, insanely fast and was decided to be used as the number utilized to calculate the weight of the minimum bandwidth number in the EIGRP formula.

    The reason that we are adding weight to each number in EIGRP is easy to understand. EIGRP is a complex formula with different sets of numbers that have varying levels of relevance. We decide how much weight, or relevance, the minimum bandwidth has by taking 10^7 (dividend) and dividing it by the minimum bandwidth (divisor), the resulting number (quotient) multiplied by 256 [Read: 2^8 ‘binary octet max value’] is your weighted bandwidth.

    “The multiplication of 256 is done so EIGRP is compatible with IGRP (the predecessor of EIGRP).”

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