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Forum Replies

  1. Hi Hussein,

    It will be shared in proportion based on the feasible distance. If the successor had a FD of 100 and the feasible successors had a FD of 20 and 10 then you'd see a 10:2:1 ratio.

    Rene

  2. Hello Rene,
    In OSPF COST is the key to manipulate traffic. What is the best way to manipulate traffic in EIGRP? Thank you so much.

    Azm

  3. Hello Azm

    It is important to clarify what COST is. The proper term for routing protocols is metric but we often use the word cost to refer to that. Each routing protocol uses a different system for evaluating the metric as you know very well. So when implementing OSPF, when you want to manipulate the way that traffic is distributed among multiple paths to a specific destination, you can tweak the metric or cost by adjusting the bandwidth parameter on the interfaces that form each path, thus changing the OSPF metric to that destination.

    The logic is similar for EIGRP. Change the metrics for each path and you can manipulate how traffic is routed. Because EIGRP evaluates the metric differently however, the procedure is a little bit more involved. You can choose from multiple parameters to tweak to get it to function as you like.

    According to Cisco:

    EIGRP updates contain five metrics: minimum bandwidth, delay, load, reliability, and maximum transmission unit (MTU). Of these five metrics, by default, only minimum bandwidth and delay are used to compute best path. Unlike most metrics, minimum bandwidth is set to the minimum bandwidth of the entire path, and it does not reflect how many hops or low bandwidth links are in the path. Delay is a cumulative value which increases by the delay value of each segment in the path. For more information on EIGRP metrics refer to the Enhanced Interior Gateway Routing Protocol White Paper.

    So, in the default configuration, to manipulate EIGRP, you can:

    1. Tweak the bandwidth parameter of one of the links in the path in question (since minimum bandwidth of a path to a destination is used to calculate metric)
    2. Tweak the delay parameter of several of the links in the path in question (since delay is cumulative on the whole link to calculate metric)

    If you want to go further, you can activate the other three metrics and use those for more granular manipulation. You can find out more about this at Cisco’s documentation: Setting a preferred route by influencing EIGRP metrics.

    I hope this has been helpful!

    Laz

  4. Hello Laz,
    Thank you so much as usual. In OSPF, manipulation of cost(ip ospf cost …) is used widely to manipulate traffic even though changing bandwidth can also be used to manipulate path. That is why I was wondering what is the best practice to manipulate path in EIGRP. Thanks once again.

    Azm

  5. Thanks a lot…you the man…

    Azm

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