Which of the following descriptions of the OSPFv3 message format are correct? (Multiple choice)

Question

Options

• AHello messages no longer contain address information and carry Interface ID
• BRemoved Authentication and Auth Type fields
• CThe OSPF version number changed from 2 to 3
• DThere is no change in the option field of the Hello message.

• A
  4% (1)
• B
  86% (24)
• D
  11% (3)

Explanation

OSPFv3 made two definitive structural changes to its packet header: it incremented the version field from 2 to 3 (C), and it dropped the AuType and Authentication fields entirely, delegating all security to IPsec at the IPv6 layer (B). These are unambiguous, verifiable header-field changes.

Why A is wrong: OSPFv3 Hello packets do add an Interface ID field, but they still carry Router IDs (32-bit identifiers for DR/BDR and neighbor lists) - so saying they "no longer contain address information" is inaccurate. The statement is half-true, which makes it a trap.

Why D is wrong: The Options field did change significantly in OSPFv3 - it was expanded from 8 bits to 24 bits and gained new flags (V6-bit, R-bit, etc.), so claiming "no change" is factually incorrect.

Memory tip: Think "OSPFv3 outsourced security and upgraded its version" - B (no auth fields, IPsec handles it) and C (v2 → v3) are the two cleanest, exam-testable header-level changes. If a choice mixes truth with error (like A), or denies a known expansion (like D), eliminate it.

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