As shown in the figure, which of the following statements is correct?

Question

Options

• AGE0/0/1 on the SWA is the backup port
• BGE0/0/2 on the SWA is an Alternative port
• CSWB will be the root bridge
• DGE0/0/1 on SWB is the root port

• A
  3% (1)
• B
  79% (26)
• C
  12% (4)
• D
  6% (2)

Explanation

In RSTP, an Alternate port is a blocked port that provides a secondary path toward the root bridge - essentially a backup for the root port. GE0/0/2 on SWA fits this role because it reaches the root bridge via SWB, while GE0/0/1 on SWA serves as the primary (root) port with the better path cost; when two paths exist to the root, the inferior one becomes the Alternate port.

Why the distractors are wrong:

• A is wrong because a Backup port backs up a Designated port on the same segment (same switch, same collision domain) - not a root port. GE0/0/1 on SWA is the root port, not a designated port needing a backup.
• C is wrong because the root bridge is elected by the lowest Bridge ID (priority + MAC address); the topology indicates SWA (or another switch) wins that election, not SWB.
• D is wrong because a root port faces toward the root bridge. GE0/0/1 on SWB most likely faces away from the root (toward SWA's segment), making it a Designated port, not a root port.

Memory tip: Think Alternate = Alternative path to the root (backs up the root port), Backup = Branch backup on the same LAN segment (backs up the designated port). If the blocked port is on a different switch from the designated port, it's Alternate; if it's on the same switch as the designated port for that segment, it's Backup.

No community discussion yet for this question.