vPC Peer Switch Feature - How many BPDUs does the downstream receive

From my understanding, both parent switches in the VPC domain act as STP roots and send BPDUs to the downstream devices. Does this mean the downstream device receives at least two BPDUs from the "same" parent? Same parent in the sense that the downstream device sees only one upstream device. 

 

Comments

  • Only the vPC Primary sends BPDUs to vPC member ports.  Peer switch only really has an effect when the vPC Primary goes down, and the Secondary becomes Operational Primary.  In that case the Secondary (now Operational Primary) starts to send BPDUs to the member ports, but it uses the same Bridge ID as the previous Primary did (because of peer-switch).

    Just keep in mind that you have to manually set the Primary and Secondary to have the same Bridge Priority, because Peer Switch only changes the MAC Address portion of the BID, not the Priority.

  • Answrer is yes. You can check the vPC Best Practices Configuration guide for further informations and you will see P.63 on vPC peer-switch you have all your answers with graphic details:

    "With vPC peer-swtich activated, STP BPDUs are directly processed by the logical Spanning Tree Protocol root
    formed by the 2 peer devices. Note that a vPC-attached access device will receive 2 BPDU: 1 per vPC peer
    device
    . The content of the BPDU is exactly the same. BPDU proxing over vPC peer-link is no more needed once
    vPC peer-switch is activated."

    In resume, "peer-switch":

    - appear as a single STP root in the Layer 2 topology

    - vPC peer link is excluded from the STP computation, with no more BPDU Proxing: STP BPDUs are sent from both vPC peer devices

    - use the same bridge ID automatically generated at the vpc domain instantiation or fixed by system-mac under vpc domain config

    hth

  • I tend to agree with p3rh0ps as if you look at the vPC best practices guide it does show both peer switches sending their bids to the CE device with peer-switch activated and the same stp configuration under the vPC domain

    their is a depiction confirming this behaviour


    On 29 May 2015, at 16:21, Brian McGahan <[email protected]> wrote:

    Only the vPC Primary sends BPDUs to vPC member ports.  Peer switch only really has an effect when the vPC Primary goes down, and the Secondary becomes Operational Primary.  In that case the Secondary (now Operational Primary) starts to send BPDUs to the member ports, but it uses the same Bridge ID as the previous Primary did (because of peer-switch).

    Just keep in mind that you have to manually set the Primary and Secondary to have the same Bridge Priority, because Peer Switch only changes the MAC Address portion of the BID, not the Priority.




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  • thank you

    On 29 May 2015 at 19:20, Brian McGahan <[email protected]> wrote:

    Only the vPC Primary sends BPDUs to vPC member ports.  Peer switch only really has an effect when the vPC Primary goes down, and the Secondary becomes Operational Primary.  In that case the Secondary (now Operational Primary) starts to send BPDUs to the member ports, but it uses the same Bridge ID as the previous Primary did (because of peer-switch).

    Just keep in mind that you have to manually set the Primary and Secondary to have the same Bridge Priority, because Peer Switch only changes the MAC Address portion of the BID, not the Priority.



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    View this message online at: http://ieoc.com/forums/p/32589/256330.aspx#256330

    Mbong Hudson,
    C.T.O VMBG Music,
    Work Email: [email protected]

  • Thanks guys... I wonder what the scalability advantage is of having both vPC peers send BPDUs... 

    On 30 May 2015 at 14:33, Sukhjit.Hayre <[email protected]> wrote:
    I tend to agree with p3rh0ps as if you look at the vPC best practices guide it does show both peer switches sending their bids to the CE device with peer-switch activated and the same stp configuration under the vPC domain

    their is a depiction confirming this behaviour


    On 29 May 2015, at 16:21, Brian McGahan <[email protected]> wrote:

    Only the vPC Primary sends BPDUs to vPC member ports.  Peer switch only really has an effect when the vPC Primary goes down, and the Secondary becomes Operational Primary.  In that case the Secondary (now Operational Primary) starts to send BPDUs to the member ports, but it uses the same Bridge ID as the previous Primary did (because of peer-switch).

    Just keep in mind that you have to manually set the Primary and Secondary to have the same Bridge Priority, because Peer Switch only changes the MAC Address portion of the BID, not the Priority.




    INE - The Industry Leader in CCIE Preparation

    http://www.INE.com



    Subscription information may be found at:

    http://www.ieoc.com/forums/ForumSubscriptions.aspx


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    View this message online at: http://127.0.0.1/forums/p/32589/256352.aspx#256352

    Mbong Hudson,
    C.T.O VMBG Music,
    Work Email: [email protected]

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