I am quite confused after doing some research online regarding designated port selection. It looked like to me that each port segment has a designated port and a blocked port? If you look at the diagram (S3) you can see that there are three segments that don't contain a blocked port... how is this possible?

  • Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin
    Dec 23, 2021 at 20:05

1 Answer 1


If the port is not the root port, and it has a better (lower) cost than the received BPDU, the port is designated, otherwise it’s blocked.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.