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Difficulty: MediumIPv6 Addressing and Deployment

A network engineer is auditing IPv6 interface configurations on a core switch. An interface is manually configured with the fully expanded IPv6 address 2001:0db8:0000:0000:00ab:0000:0000:0001/642001:0\text{db8}:0000:0000:00\text{ab}:0000:0000:0001/64. According to standard RFC 5952 zero-compression and leading-zero suppression rules, which of the following represents the correct canonical form of this address?

  1. 2001:db8::ab:0:0:1/64Answer
  2. B
    2001:db8::ab::1/64
  3. C
    2001:db8:0:0:ab::1/64
  4. D
    2001:0db8::ab:0:0:1/64

Answer

The canonical form of the address is 2001:db8::ab:0:0:1/64.
According to RFC 5952 guidelines for canonical IPv6 address formatting: 1) Leading zeros in any hextet must be omitted (0db8 becomes db8, 00ab becomes ab, 0001 becomes 1). 2) The double-colon (::) must be used to shorten contiguous zero hextets. 3) If there are multiple zero sequences of equal length, the first sequence must be compressed using double-colon, leaving subsequent zero hextets represented as single zeros. Applying these rules yields 2001:db8::ab:0:0:1/64.

Step-by-Step Solution

1
Suppress leading zeros in each 16-bit hextet.
2001:0db8 becomes 2001:db8, 0000 becomes 0, 00ab becomes ab, and 0001 becomes 1.
RFC 5952 mandates that leading zeros within each hextet must be suppressed.
2
Identify contiguous sequences of zero hextets.
Sequence 1 contains two zeros (hextets 3 and 4); Sequence 2 contains two zeros (hextets 6 and 7).
Double-colon zero compression can only be applied to contiguous sequences of all-zero hextets.
3
Apply the double-colon (::) operator to compress zero hextets according to tie-breaking rules.
Compress Sequence 1 to yield 2001:db8::ab:0:0:1/64.
When zero sequences are equal in length, RFC 5952 Section 4.2.3 requires compressing the first sequence, and double-colon can only be used once per address.

Key Concept

RFC 5952 IPv6 Address Representation and Compression Rules
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Topics

IPv6 Addressing and Deployment

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