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ip fabric design

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  • 1.  ip fabric design

    Posted 10-23-2018 04:17

    Hi All,


    I have a general question about capacity planning when it come with deploing an IP Fabric scenario:
    Assuming I have:
    - qfx5200-32c -> 32x100Gbps interfaces -> Spine
    -  qfx5200-48y ->  Leaf

    In theory to this spine I can connect up to 32 qfx5200-48y (100 Gbps uplink).

    Each leaf than have 48 x 10Gbps access interfaces.

    Question: I need to understand the correct approach on how to calculate the max numbers of leaf that can be connected to one spine. I am sure that oversubscription and maximum throughput for each single switch play a role but i am not sure how to combine them to roll out some numbers.

    Any suggestion?

    Thank you.

  • 2.  RE: ip fabric design

    Posted 04-05-2019 02:55

    Good day,


    We have very useful document for VCF.

  • 3.  RE: ip fabric design
    Best Answer

    Posted 04-05-2019 06:04



    Calculation is as following:

    Each leaf has 48x10Gbps access ports, which gives  480Gbps of total bandwidth.

    In order to have no oversubscription, you need 5x100Gbps uplink ports.

    If you have one spine, then you can connect 6 leafs with no oversubscription. 

    With ovesubscrioption model, you can connect 32 leafs with 4,8:1 ratio,  16 leafs with 2,4:1 ratio, 8 leafs with 1,2:1 ratio.


    In order to scale, you would need to add spines. With 2 spines you can connect 10 leafs with no oversubscription and so forth.