STP question

[adriansilivestru]

I am confused about the below answer.

I was under the impression that a port is put into the discarding state following the below steps in order:

1) Cost to root bridge

2) Lowest BID

3) Port priority

4) Port ID

In the below question, shouldn't the answer be "lowest sending BID" since the BID is composed of priority and MAC address and it's pretty much impossible for two switches to have the same MAC address ?

[rais]

C is correct.  It's not about switches - which one is going to be root. That's already done. It has come down to two competing links.

How about two ports of the same switch connected via a cable.

HTH.

[Jaderson Pessoa]

Hello,
The correct answer is C, because they are talking about PORT ID, in this case, root bridge is already choosen, but there are two links and only one need be as active while other in standby (discarging) state. The higher port will select to be as forwarding state.

But this process occurs because the speed is the same for both links.

Regards,