STP root guard; how it works

Discussion in 'Cisco' started by jwstric2, Feb 16, 2009.

  1. jwstric2

    jwstric2

    Joined:
    Feb 13, 2009
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    From cisco's page about spanning tree: "No traffic passes through the port in this state. After device D ceases to send superior BPDUs, the port is unblocked again. Via STP, the port goes from the listening state to the learning state, and eventually transitions to the forwarding state. Recovery is automatic; no human intervention is necessary."



    1. In STP election, when will a new device stop sending superior BPDUs (the device that is being "blocked" by a root guarded port.
    2. In relation to question 1, what will the new device act as (who does it assume the root bridge is; does it accept the higher cost root bridge.
    jwstric2, Feb 16, 2009
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  2. jwstric2

    donjohnston

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    I think you're assuming that device D automatically stops sending superior BPDU's. It doesn't. The configuration has to be changed so the bridge priority is higher than the current root.
    donjohnston, Feb 19, 2009
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