200-301 Question #626: Real Exam Question with Answer & Explanation

Question

Drag and Drop Question Drag and drop the IPv6 addresses from the left onto the corresponding address types on the right. Answer:

Explanation

IPv6 Address Classification Explanation

The Two Address Types

Global Unicast (GUA) — Publicly routable addresses. Defined by prefix 2000::/3, meaning the first 3 bits are 001. This covers the hex range 2000:: through 3fff::.

Unique Local (ULA) — Private, non-routable addresses (analogous to IPv4's RFC 1918 space). Defined by prefix fc00::/7, meaning the first 7 bits are 1111 110. This covers addresses starting with fc or fd.

Individual Placements

2001:db8:600d:cafe::123 → Global Unicast Starts with 2001. In binary: 0010 0000... — first 3 bits are 001, placing it in 2000::/3.

Common misconception: 2001:db8::/32 is the documentation/example prefix (RFC 3849). Exam questions frequently use it as a GUA example anyway, and structurally it is a GUA by prefix rules.

3ffe:e54d:620:a87a::f00d → Global Unicast Starts with 3ffe. In binary: 0011 1111... — first 3 bits are still 001, so it falls within 2000::/3.

Note: 3ffe::/16 was the old 6bone experimental prefix, deprecated by RFC 3701. However, it is still classified as GUA structurally. Exams test the prefix rule, not historical deprecation.

fcba:926a:... → Unique Local Starts with fc. In binary: 1111 1100 — first 7 bits are 1111 110, matching fc00::/7.

fd6d:c83b:... → Unique Local Starts with fd. In binary: 1111 1101 — first 7 bits are also 1111 110, matching fc00::/7.

Quick Identification Rules

Common Mistakes

• Confusing fc vs fd: Both are ULA. The fd prefix means the Global ID was locally generated (L-bit set); fc means centrally assigned. Both map to Unique Local on exams.
• Dismissing 3ffe as non-GUA because 6bone is deprecated — structurally it is still GUA by the 2000::/3 prefix rule.
• Treating 2001:db8:: as special — it's documentation-only but still classified as GUA for exam purposes.

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