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Difficulty: MediumIPv6 Addressing Concepts and Header Structure

A network administrator is documenting IPv6 address assignments for an enterprise network. Which of the following are syntactically valid IPv6 address representations for the uncompressed address `2001:0db8:0000:0000:0000:0000:0000:0001`? (Select TWO.)

  1. 2001:db8::1Answer
  2. 2001:db8:0:0:0:0:0:1Answer
  3. C
    2001:db8::0::1
  4. D
    2001::db8::1

Answer

The syntactically valid representations are '2001:db8::1' and '2001:db8:0:0:0:0:0:1'.
The representation '2001:db8::1' is valid because it suppresses the leading zero in '0db8' to 'db8' and replaces six consecutive zero hextets with a single double colon (::). The representation '2001:db8:0:0:0:0:0:1' is also valid because it reduces each '0000' hextet to a single '0' and suppresses the leading zero in '0db8' without invoking double-colon compression rules.

Step-by-Step Solution

1
Evaluate leading zero suppression rules for 16-bit hextets.
Leading zeros in any hextet can be omitted (e.g., '0db8' becomes 'db8', and '0000' becomes '0').
IPv6 standard formatting permits suppressing leading zeros within individual 16-bit fields without altering address value.
2
Evaluate zero compression rules using double-colon notation (::).
A single double colon (::) can represent contiguous groups of zero hextets, but it can only appear ONCE in an address.
Multiple double colons introduce structural ambiguity, preventing network devices from determining the precise number of missing zero fields.
3
Verify candidate address formats against syntactic rules.
'2001:db8::1' correctly uses a single double colon for six zero hextets, while '2001:db8:0:0:0:0:0:1' correctly suppresses leading zeros without double-colon compression.
Only options that strictly adhere to single-instance double-colon compression and valid leading-zero omission are syntactically valid.

Key Concept

IPv6 Address Compression and Syntax Rules
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Topics

IPv6 Addressing Concepts and Header Structure

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