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Forum Replies

  1. Hi Francesco,

    EIGRP will store all the possible paths in its topology table, between the brackets it stores the FD (feasible distance) and AD (advertised distance). For example:

    (156160/128256)

    156160 = feasible distance
    128256 = advertised distance

    Sometimes they use "computed distance" to refer to feasible distance and "reported" distance to refer to the advertised distance.

    In the topology table you will find at least 1 successor and possible some feasible successors. To become a feasible successor, its AD has to be lower than the FD of the successor.

    Hope this helps!

    Rene

  2. Hello Rene,
    I Know, I know
    the problem now is this:

     Jack#show ip eigrp topology 
    P 2.2.2.0/24, 1 successors, FD is 156160
            via 192.168.12.2 (156160/128256), FastEthernet0/0

    I understand your explanation, is only that in the new guide they say about the value FD 156160 is an historical copy since a distance pass from active to passive.
    This value is internal and never pass to neigbors, it could only decrease and is this that we check for FC.....
    they call (156160) first valure in the bracket ..computed distance and this is that a router pass to neigbor...so they say that is not always true that if a router has more FS it chose that one meet the FC......

  3. Hi Hussein,

    1. The route will become "active" first and then the router will start sending query packets.
    2. The "U" for update means that an update packet has been sent to this destination.
    3. The "R" for reply means that an update packet has been sent to this destination.

    You'll have to be fast to actually see the update and reply status in the EIGRP topology table as this happens really fast, it will be easier to see this process by enabling a debug.

    Rene

  4. Hi Rene,

    How does EIGRP come up with the local metric for the interface it's using to reach the destination network? And where can we see it. Thank you

  5. Hi Victor,

    EIGRP uses this formula to calculate the metric:

    https://networklessons.com/eigrp/eigrp-k-values-formula/

    Here is an example of a directly connected gigabit interface with a network that is advertised in EIGRP:

    R1#show ip eigrp topology 192.168.12.0/24
    EIGRP-IPv4 Topology Entry for AS(1)/ID(11.11.11.11) for 192.168.12.0/24
      State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2816
      Descriptor Blocks:
      0.0.0.0 (GigabitEthernet0/1), from Connected, Send flag is 0x0
          Composite metric is (2816/0), route is Internal
          Vector metric:
            Minimum bandwidth is 1000000 Kbit
            Total delay is 10 microseconds
            Reliability is 255/255
            Load is 1/255
            Minimum MTU is 1500
            Hop count is 0
            Originating router is 11.11.11.11

    You can see the metrics that are used for the formula (bandwidth and delay by default) and the FD which is 2816.

    Rene

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