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  1. Hi Rene,

    I am not clear about the root bridge. I mean why are we finding the root port(for non-root bridge) to reach the root bridge. Is it like in practical scenario, the root bridge is set as destination to one of the server?

  2. Hi Rene,

    I have a question to the description on the third topology. You say:

    “SW3 will receive BPDUs on its 10 Mbit interface (cost 100) and on its 1000 Mbit interface (cost 4). It will use its 1000 Mbit interface as its root port.”

    Should SW3 receive on 10Mbit interface BPDUs of 0 instead of 100 because they are generated by the root? And then SW3 add its port cost of 100 and send it to SW4 and SW5?

    Is it correct that the BPDU sending SW don’t add the costs of the outgoing interface/link, only the links that left behind? So the receiving SW has to add the cost of the link where it receives the bpdu and then it will forward?

    thanks and regards

  3. Hello Laz,
    I have one question and I am going to use the below topology.



    In this scenario, I have switch 1 connected to switch 2 through two Fast Ethernet links as it is drawn above. Switch 1 is the root bridge. Switch 2 has to pick one link between fa0/1 and fa0/2 links as the root port and block another one. Therefore, Switch 1 will look at the cost of fa0/1 and fa0/2 links and they both are the same which is 19. Now Switch 1 will look at the port priority of fa0/1 and fa0/2, but they both are the same which is 128 by default. So Switch 1 will now look at the port numbers and since fa0/1 is lower than fa0/2 Switch 1 will pick fa0/1 as the root port and block fa0/2.

    If fa0/2 had a port priority of 16 and fa0/1 had a port priority of 128, would fa0/2 not become the root port? As far as my understanding goes, fa0/2 should become the root if it has a port priority less than fa0/1.

    However, I have read somewhere, in order to influence the local switch port, the port-priority change has to be done in the upstream switch. In this case Switch 1. I have tried this in my lab and fa0/2 becomes the root port only when I change the port priority of fa0/22 on Switch 1. Would you please explain it to me at your convenient time? Thank you so much.


  4. Hi Rene,

    Could you just explain me the ports roles and states for your mentioned diagram. I have understood about the root port election but i am confused with roles and states. Thanks in advance.


  5. Hi Laz,
    great, thank you very much

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