Question NA348

[ryanf]

Just wondering if the answer should be "Switch4, port fa0/11"?

[kbates]

Same here. If switch 4 is receiving lower BPDUs on Fa0/2 from switch 3 on port Fa0/1 (lower port index), wouldn't that put Fa0/11 on switch 4 in the blocking state?

[jakesteramma]

I agree with you guys. According to the following literature I found online, the port with the "Lowest Sending Port ID" is elected ROOT!! Therefore, Port Fa0/11 on Switch 4 should assume the discarding role.


The following criteria are used by each spanning tree node to select a path to the root bridge:

  1. Lowest root bridge ID - Determines the root bridge
  2. Lowest cost to the root bridge - Favors the upstream switch with the least cost to root
  3. Lowest sender bridge ID - Serves as a tie breaker if multiple upstream switches have equal cost to root
  4. Lowest sender port ID - Serves as a tie breaker if a switch has multiple (non-Etherchannel) links to a single upstream switch