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Difficulty: MediumIPv6 Addressing Concepts and Header Structure

A network engineer is inspecting an interface configuration on a core router. The uncompressed 128-bit IPv6 address assigned to the interface is 2001:0db8:0000:0000:0008:0000:0000:00012001:0db8:0000:0000:0008:0000:0000:0001. According to standard IPv6 address compression rules (RFC 5952), which of the following is the correct shorthand representation of this address?

  1. 2001:db8::8:0:0:1Answer
  2. B
    2001:db8::8::1
  3. C
    2001:db8:0:0:0008::1
  4. D
    2001:db80::8:0:0:1

Answer

The correct compressed IPv6 address is 2001:db8::8:0:0:1.
The address 2001:db8::8:0:0:12001:db8::8:0:0:1 correctly applies RFC 5952 guidelines: leading zeros within each hextet are truncated (0db8→db80db8 \rightarrow db8, 0008→80008 \rightarrow 8, 0000→00000 \rightarrow 0), and the double-colon (::) is used exactly once to replace the first contiguous block of zero hextets (0:00:0).

Step-by-Step Solution

1
Omit leading zeros in each 16-bit hextet.
The original address 2001:0db8:0000:0000:0008:0000:0000:00012001:0db8:0000:0000:0008:0000:0000:0001 simplifies to 2001:db8:0:0:8:0:0:12001:db8:0:0:8:0:0:1.
Leading zeros within a four-digit hexadecimal group do not add value and can be safely suppressed.
2
Identify consecutive zero hextet runs to apply the double-colon (::) operator.
There are two zero runs of equal length (two groups of zeros each): 0:00:0 after db8db8, and 0:00:0 after 88.
RFC 5952 specifies that when zero runs are of equal length, the first contiguous run of all-zero hextets must be replaced with '::'.
3
Apply the double colon to the first run of zero hextets only.
The final compressed address is written as 2001:db8::8:0:0:12001:db8::8:0:0:1.
The double colon (::) can only be used once in an IPv6 address to prevent ambiguity during address expansion.

Key Concept

IPv6 Address Compression Rules (RFC 5952)
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Topics

IPv6 Addressing Concepts and Header Structure

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