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Connecting switch stacks

This thread has been viewed 11 times
  • 1.  Connecting switch stacks

    Posted Mar 22, 2024 10:33 AM

    I have two 2930M stacks on two floors of our building. Looking for advice on best way to connect them (or not to?). I do have fiber available in both locations. Ideally will share VLANs. Thx in advance.



  • 2.  RE: Connecting switch stacks

    MVP GURU
    Posted Mar 22, 2024 11:03 AM

    One stack on each floor of the same building? probably the most reliable way to interconnect them would be by using Fiber Optic cables (at least a pair), so you need SFP+ Transceivers (supposing you want to go with 10Gbps bandwidth). Having two or more FO OM4 cables (say with a total run shorted than 300 meters) you can then aggregate the involved physical interfaces together (using LACP, as example) to gain in resiliency and redundancy (and better bandwidth usage). VLANs can be then "transported" between the two stacks.




  • 3.  RE: Connecting switch stacks

    Posted Mar 22, 2024 01:49 PM

    Thanks for reply. Stacks are on contiguous floors, fiber strands have been run and I have SFPs and FO cables in-hand. Would you recommend VSF to aggregate the units into a virtual single stack? Any downfalls or unreasonable risks involved? This is a greenfield network at present, so all options on the table.




  • 4.  RE: Connecting switch stacks

    MVP GURU
    Posted Mar 22, 2024 02:23 PM
    Hi! if there aren't particular connectivity restrictions (the Fiber Optic cabling between floors is under your full control = stability/maintenance/deployability standpoint) there isn't a particular reason to avoid setting up a VSF stack with its members "distributed" between different floors but, IMHO, you should at least provide the VSF with (a) the same level of bandwidth between any VSF neighbours (say all 10G or say all 1G <- the higher the better) and (b) a Ring Topology (with multiple VSF Links between VSF neighbours, the more the better)...that's to avoid issues caused by (1) bottlenecks for traffic which could potentially traverse all the stack to reach its destination (not all traffic will stay local in a particular VSF member where it is originated) and (2) an undesired split brain scenario when VSF topology breaks (-> deploy a VSF MAD mechanism to mitigate).

    Also consider that a simple software update (say you want to perform VSF management by applying a software update from time to time) implies that the whole stack reboots (all VSF members reboot concurrently -> expdct a downtime for all connected peers...no matter if peers are multi-homed with LACP Links Aggregation against the VSF members).

    So you have to carefully evaluate pro/cons based on your specific requirements (say...you want an easy configuration) and restrictions (say...you want no downtime during software updates).

    In any case there is a large documentation base about how to correctly deploy and manage an ArubaOS-Switch based VSF stack (best practice guide).