200-301 · Question #1273
Refer to the exhibit. All switches are configured with the default STP priorities. During the STP elections, which switch becomes the root bridge if all interfaces are in the same VLAN?
The correct answer is B. MDF-DC-2: 0d:0E:18:1B:05:97. In an STP election with default switch priorities, the switch with the lowest MAC address is chosen as the root bridge.
Question
Options
- AMDF-DC-1: 0d:E0:43:96:02:30
- BMDF-DC-2: 0d:0E:18:1B:05:97
- CMDF-DC-4: 0d:E0:19:A1:B3:19
- DMDF-DC-3: 0d:0E:18:2A:3C:9D
How the community answered
(57 responses)- A2% (1)
- B81% (46)
- C12% (7)
- D5% (3)
Why each option
In an STP election with default switch priorities, the switch with the lowest MAC address is chosen as the root bridge.
0d:E0:43:96:02:30 is a numerically higher MAC address than 0d:0E:18:1B:05:97, so it would not be elected root with default priorities.
When all switches are configured with the default STP priority (32768), the Spanning Tree Protocol elects the switch with the numerically lowest MAC address as the root bridge, and 0d:0E:18:1B:05:97 is the lowest among the given options.
0d:E0:19:A1:B3:19 is a numerically higher MAC address than 0d:0E:18:1B:05:97, so it would not be elected root with default priorities.
0d:0E:18:2A:3C:9D is a numerically higher MAC address than 0d:0E:18:1B:05:97, so it would not be elected root with default priorities.
Concept tested: STP root bridge election process
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10556-16.html
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