How are the different versions of IGMP compatible?

Question

Options

• AIGMPv2 is compatible only with IGMPv1.
• BIGMPv2 is compatible only with IGMPv2.
• CIGMPv3 is compatible only with IGMPv3.
• DIGMPv3 is compatible only with IGMPv1

• A
  86% (18)
• B
  10% (2)
• C
  5% (1)

Explanation

IGMP Version Compatibility

Option A is correct because IGMPv2 was designed with backward compatibility in mind, specifically with IGMPv1 only - when an IGMPv2 router detects IGMPv1 hosts on a network segment, it adjusts its behavior to interoperate with them, but it does not natively extend this compatibility upward to IGMPv3 without additional mechanisms.

• Option B is wrong because IGMPv2 is not limited to communicating only with itself; its backward compatibility with IGMPv1 is a core design feature.
• Option C is wrong because IGMPv3 is actually backward compatible with both IGMPv2 and IGMPv1, not restricted to IGMPv3 only.
• Option D is wrong because while IGMPv3 can work with IGMPv1, it is not exclusively limited to IGMPv1 - it supports compatibility across all earlier versions.

Memory Tip: Think of IGMP versions like software updates - each newer version looks back to support older versions, but the key exam point is that IGMPv2's specific defined backward compatibility target is IGMPv1, while IGMPv3 has broader compatibility. Remember: "v2 looks back one step to v1."

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