How many packets are needed to establish IKEv1?

Question

Options

• AOnly three packets for main mode
• B8
• C5
• D6

• A
  7% (3)
• B
  2% (1)
• C
  2% (1)
• D
  88% (36)

Explanation

IKEv1 Main Mode requires exactly 6 packets - three bidirectional exchanges of 2 packets each: SA proposal/response, Diffie-Hellman key exchange, and encrypted authentication. This makes D correct as the standard packet count for establishing an IKEv1 Phase 1 tunnel.

Why the distractors are wrong:

• A (3 packets for Main Mode) - 3 packets is actually the count for Aggressive Mode, not Main Mode; the answer confuses the two IKEv1 modes.
• B (8) - no standard IKEv1 exchange uses 8 packets; this is simply incorrect.
• C (5) - not a valid packet count for any standard IKEv1 mode; likely a trap for off-by-one errors.

Memory tip: Think "6 = 3 rounds × 2" - Main Mode has 3 exchanges and each is a back-and-forth (request + response), giving you 6. If you see "3 packets," that's Aggressive Mode trading security for speed.

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