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Difficulty: MediumIPv6 Addressing Concepts and Header Structure

A network administrator is assigning IPv6 link-local addresses to server interfaces within a local subnet. The administrator must ensure that the configured addresses belong to the link-local scope (fe80::/10fe80::/10) and adhere strictly to standard IPv6 shorthand compression rules. Which of the following represents a valid IPv6 link-local address in compressed format?

  1. fe80::20c:99Answer
  2. B
    fe80::1000::99
  3. C
    fe80:0000:0000:00000:0000:0000:020c:0099
  4. D
    2001::20c::99

Answer

The address fe80::20c:99 is the valid IPv6 link-local address formatted according to standard zero-compression rules.
The valid choice correctly identifies the link-local prefix (fe80::/10) and applies zero-compression rules properly by utilizing a single double-colon (::) to collapse consecutive zero hextets, ensuring a non-ambiguous 128-bit IPv6 address.

Step-by-Step Solution

1
Identify the required prefix scope for link-local addresses.
Link-local addresses reside in the prefix range fe80::/10 (typically starting with fe80::).
Ensures the address is designated strictly for single-link communications.
2
Evaluate the address syntax rules defined by RFC 5952.
A single contiguous sequence of zero-valued 16-bit fields may be replaced by double colons (::) exactly ONCE in an address. Each hextet can have at most 4 hexadecimal digits.
Prevents ambiguity when expanding the compressed 128-bit address back to its full representation.
3
Compare candidate addresses against scope and compression rules.
The address starting with fe80 and containing a single double-colon (fe80::20c:99) satisfies all formatting requirements.
All other choices either use multiple double-colons or invalid hextet digit counts.

Key Concept

IPv6 Link-Local Addressing and RFC 5952 Compression Rules
Estimated Time:1m 0s
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Topics

IPv6 Addressing Concepts and Header Structure

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