The BFD sending interval of BFD packets is _____ milliseconds, the receiving interval is _____ milliseconds, and the local detection is _____ times.

Question

Options

• A1000|1000|3
• B50|50|3
• C100|100|3
• D10|10|3

• A
  79% (34)
• B
  2% (1)
• C
  7% (3)
• D
  12% (5)

Explanation

Option A is correct because the default BFD (Bidirectional Forwarding Detection) parameters, as defined in standard implementations (including Huawei networking equipment, which this question targets), are a minimum transmit interval of 1000ms, a minimum receive interval of 1000ms, and a detection multiplier of 3. This means the local detection timeout is 1000 x 3 = 3000ms before a session is declared down. Options B (50ms), C (100ms), and D (10ms) represent valid configurable BFD intervals that can be set for faster failure detection, but they are not the default values - they are common in tuned environments where sub-second detection is required. The distractors are plausible precisely because BFD is often praised for its fast hello timers, which tempts exam takers to assume a small default.

Memory tip: Associate BFD defaults with the phrase "one second, three strikes" - packets are sent every 1000ms, and after 3 missed packets (3 x 1000ms = 3 seconds), the neighbor is declared unreachable.

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