STP Confusion: 4 Switch Network

[yodaddy0125]

Good Afternoon,

I am trying to get some assitance on determining theoretically the correct way STP will block the ports on a 4th switch in a simple network topology. I know the tie breaker rules just dont fully understand them for the bottom switch. We are being taught that the bottom Switch bases it decision off of rule 4 (Lowest Port ID) because rule 3 Sender Bridge ID is local to it self. So FA 0/1 will be the DP and FA 0/2 will blocked on bottom switch. Instead of the other way arround, is this correct and is there any way to better explain this.

I assumed that FA 0/2 would be the Root port and FA 0/1 would be blocked becuase the right siwthch has a lower bridge id and that is where the BPDU are originating from.

[GRANT3779]

Has this been labbed up and tested to see which port does become root?

What are the Switch priorities of the switch on Left and Right? Are they the same / default setting?

My understanding from the given topology is that your bottom switch will currently have equal cost to the root bridge from each port.

If this is true then the next process for root port selection is to select the port that has the neighbour with the lowest Bridge ID. Assuming default priorities then Fa0/2 would be Root Port.

If Fa0/2 is not root port then I would double check the switch priorities on two side switches (remember the Bridge ID is made up of 2 parts)