12-14-2009, 06:11 PM
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
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