EIGRP Unequal Cost Load Balancing

Lessons Discussion
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19 posts were merged into an existing topic: EIGRP Unequal Cost Load Balancing

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Excellent post. Explained better than Jeff Doyle in TCP/IP Vol 1.
Thanks Rene. Appreciate your hard work.

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Thanks for this post Rene. Iā€™m studying for my ICND2 exam and it is VERY difficult to find a person who explains a difficult topic in terms the normal human being can understand. Very glad I stumbled across this site.

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Iā€™m glad you like it Kyle! Good luck studying.

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I have a question, Do load balancing occur automatically in some cases ? or we have to do by giving commands, just like setting variance, and making the FD of successor greater than the FD of feasible successor? please make me clear regarding this, I am confused regarding this thing
and I have found your EIGRP explanation marvelous among all stuff available in the internet.

Thanks

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Hi Khurram,

When there are 2 paths with the same metric, EIGRP will select both and it will perform equal-cost load balancing. If you want unequal cost-load balancing youā€™ll have to make sure you have a feasible successor and change the variance command.

Rene

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I think itā€™s gonna be easier if we divide de FD of the FS by the FD of the Sā€¦like 109/10=10.9 and we choose a multiplier equivalent like 11ā€¦ what do you think?

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Yes thatā€™ll work and itā€™s easier.

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Sir than what is king Kong Successor or Feasible successor n I just want to ask u is Is load balancing is like choosing shortest path like u choose 109 instead of 110 is it ???

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Sir is load balancing is like choosing shortest path between 109 and 110 is it ???

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If i remove variance command what will happen? Who will become a successor and feasible successor?

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Variance is only used to activate unequal cost load balancing. The successor and feasible successor remains the same.

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Router KingKong is neither because it doesnā€™t pass the ā€œfeasible successorā€ rule. This post explains exactly how it works:

Normally a routing protocol selects the best path and uses that for all traffic. Load balancing occurs when there are two equally best paths (traffic will be sent 50/50). In case of EIGRP, it can do unequal load balancing like this post explained.

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suppose i have three routers. topology is as follows:

         R1
     /       
    /         
 R2 ---------R3

trio are connected each other with R1 ā€”R2 with T1 link
R1ā€”R3 with T1 link
R2----R3 with 512Kbps bandwidth.all other parameter are common. then according to EIGRP to reach R2 to R3 it will take path R2ā€”>R1ā€”>R3. why it will take these path. if i want to communicate between R2 to R3 directly what will i do.

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Hi Shashank,

In your picture it shows R1 connected to R2 but you mean that R1 is connected to R3 right?

If you want to influence EIGRP then you can change the bandwidth on one of the links. You could set the bandwidth of the 512Kbps link to 2048Kbps or something and then EIGRP will select that path. This might not be a good solution since in reality, passing two T1 links is a higher bandwidth path than the 512Kbps link but you can do it.

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Great explanation on variance in the simplest way ever. Thanks Rene!

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Another awesome explanation. Keep going.

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Thatā€™s good to hear :slight_smile:

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Hi Rene,
Since you used multiplier 11 , is it Load Balancing is 1:11 ie traffic through Successor will 11 times more than Feasible successor link..?

Thank You.
Pradeep K

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19 posts were merged into an existing topic: EIGRP Unequal Cost Load Balancing