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Difficulty: EasyIPv6 Addressing Concepts and Header Structure

During a routine network audit, a system administrator needs to record the correctly compressed shorthand format of the IPv6 address `fe80:0000:0000:0000:020c:29ff:fe0c:4171`. Which of the following is the correct compressed representation of this address?

  1. fe80::20c:29ff:fe0c:4171Answer
  2. B
    fe80::020c:29ff:fe0c:4171
  3. C
    fe80:0:0:0:20c:29ff:fe0c:4171
  4. D
    fe80::20c:29ff::fe0c:4171

Answer

The correct compressed IPv6 address is `fe80::20c:29ff:fe0c:4171`.
The correct representation `fe80::20c:29ff:fe0c:4171` follows RFC 5952 standard compression rules: it collapses the four consecutive all-zero 16-bit fields (`0000:0000:0000:0000`) into a single double colon `::`, and suppresses the leading zero in `020c` to `20c`.

Step-by-Step Solution

1
Identify leading zeros in each 16-bit field (hextet) and drop them.
The field `020c` becomes `20c`. Fields with single `0000` become `0`.
IPv6 syntax rules require dropping leading zeros within any individual 16-bit hexadecimal block.
2
Locate the longest contiguous run of all-zero fields.
The sequence `:0000:0000:0000:` consists of four consecutive zero hextets.
Standard IPv6 zero-compression replaces the longest consecutive run of zero fields with a double colon `::`.
3
Apply the double colon (`::`) exactly once to replace the consecutive zero fields.
The full compressed string becomes `fe80::20c:29ff:fe0c:4171`.
Using `::` more than once makes it impossible to determine how many zero fields belong to each `::` section.

Key Concept

IPv6 Address Compression Syntax (RFC 5952)
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Topics

IPv6 Addressing Concepts and Header Structure

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