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Forum Replies

  1. Why does the Root switch has the port Fa0/17 Blocked in the example “Spanning-Tree Disabled”?
    Isn’t that said, that all ports of the root switch should be designated?

    If we disable spanning-tree on SW3 (for VLAN 10), then I guess the SW3 should be transparent for spanning-tree: as if the SW1 would be connected directly with SW2 on all four ports.

  2. Hello Lukasz

    The diagram that you are referring to indicates that port Fa0/17 is a backup port. This is a port role that is available on RSTP (802.1w). It is one of the two types of port roles that exist for the blocking state. So yes, in essence, this port is in a blocking state.

    However, keep in mind that since SW3 does not have spanning-tree activated, as mentioned in the lesson, the STP topology has not converged. A root bridge will have all designated ports once the topology has converged. So essentially, STP root bridge selection has not been complet

    ... Continue reading in our forum

  3. Hi Laz,

    but should not be the Backup port be an Alternate port then?
    I thought backup ports only exists if the switch sees its own BPDUs, which is the case if both ports would be connected to the same collision domain? But that’s not the case here!? Or was this here just used as an example for a “blocking port”?


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