As shown in the figure, in the dual-link cold standby load sharing network, the configuration is as shown in the figure, AP1 has been online, and AC1 and AP1 have established a main line. When the…

Question

Exhibit

Options

• A120 seconds
• B130 seconds
• C145 seconds
• D155 seconds

• A
  10% (2)
• B
  85% (17)
• C
  5% (1)

Explanation

In dual-link cold standby, the AP detects primary link failure via CAPWAP echo (keepalive) packets. Based on the configuration shown (echo interval × max retries), the primary failure detection completes at approximately 120 seconds. After detection, the AP begins reconnecting to the backup AC (AC2), but this reconnection process has its own retransmission windows - a first attempt window and, if that fails, a second attempt window.

B (130s) is correct because 130 seconds falls within the first valid reconnection window: the primary failure was just detected at ~120s, and the AP can complete its backup connection approximately 10 seconds later.

D (155s) is correct because if the first reconnection attempt does not complete in time, a second CAPWAP discovery/join cycle begins, and ~155 seconds falls within that second valid window for switchover completion.

A (120s) is wrong because at exactly 120 seconds, the echo retries have just concluded and the primary link has just been declared failed - the backup switchover process has not yet started, let alone completed.

C (145s) is wrong because it falls in the dead zone between the first reconnection window closing and the second CAPWAP retransmission attempt completing - the AP is mid-retry and the switchover has not yet finalized.

Memory tip: Think "detect, then two windows." The clock starts at link break, switchover cannot happen until after the full detection period (all echo retries exhausted), and then it can only occur during the CAPWAP reconnection windows - not in the gap between retry cycles or before detection finishes.

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