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  • 1.  VXLAN and Spanning Tree

    Posted Apr 04, 2023 07:46 AM

    How does loop prevention work with vlans streched using VXLAN? Will bgp evpn prevent it. I have two datacenter where I am going to deploy Aruba-CX devices and quite lot of of fibers between them. Things happen so what will happen when someone connects an access port with some vlan in one DC with a port with te same vlan (streeched by evpn)  in the second DC? Or, in even worse scenario, there will be  some switch (running spanning tree) involved along the way.



  • 2.  RE: VXLAN and Spanning Tree

    Posted Apr 04, 2023 09:05 AM

    Hi tommyd

    BPDUs are not transported over VXLAN. So there will be two separate topologies from a spanning-tree point of view. 

    This leaves you indeed with a risk of having loops in between if you manage to connect switchport in one DC to a switchport in the same vlan in the other DC. However, is that even possible? Your fibers perhaps only transport the underlay networks between the DCs not the overlay ones. And connecting an access port on an access switch in one location to another access port on an access switch in the second location doesn't seem feasible. 

    So in a properly managed network I personally don't see that much of a risk for loops across the fabric.

    Do you think differently?

    Regards, 
    Thomas


    Original Message


  • 3.  RE: VXLAN and Spanning Tree

    Posted Apr 04, 2023 09:21 AM

    >  Your fibers perhaps only transport the underlay networks between the DCs not the overlay ones.

    Not only underlay. Underlay links are separate but other fibers are used for other things like HCI storage backend management network etc. 

    > So in a properly managed network I personally don't see that much of a risk for loops across the fabric. 

    I have seen a L2 Loop around the city, at an ISP I know, witch was a result of some wrong connection on a 20km run with few splices. 

    So the conclusion is to be carefull 


    Original Message


  • 4.  RE: VXLAN and Spanning Tree

    Posted Apr 04, 2023 11:10 AM

    I learned a lot on EVPN-VXLAN in this video series.



    ------------------------------
    Herman Robers
    ------------------------
    If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.

    In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
    ------------------------------

    Original Message


  • 5.  RE: VXLAN and Spanning Tree

    Posted Apr 05, 2023 05:07 AM

    > I learned a lot on EVPN-VXLAN in this video series.

    I watched those few times and used it (and a lot of help from this community) to configure my setup. But my question was a bit to exotic.. 


    Original Message


  • 6.  RE: VXLAN and Spanning Tree

    Posted Apr 05, 2023 05:39 AM

    So what confuses me a bit is the fact that you run VXLAN across your DC borders and in parallel still have fibers connecting parts of your (overlay?) networks directly from DC1 to DC2. I actually don't see the idea behind. Maybe you have a conceptual drawing?

    Anyway, the networks which are transported L2 across DC borders can run spanning-tree or any other loop-prevention mechanism to avoid any problems coming from possible loops. 

    Regards, 
    Thomas


    Original Message


  • 7.  RE: VXLAN and Spanning Tree

    Posted Apr 05, 2023 07:04 AM

    As I wrote, there is independent network used as a HCI backend and some more fiber to connect buildings  in various parts of the city

    The simplified drawing


    Original Message


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