Examkin

Question

Difficulty: HardIPv6 Addressing Concepts and Header Structure

A network engineer is auditing IPv6 static route configurations on a core dual-stack router. During the review, the engineer identifies several shorthand IPv6 address representations. Which of the following IPv6 address representations is syntactically invalid?

  1. A
    2001:db8:0:10::1
  2. B
    fe80::ab12:0:4
  3. 2001:db8::ac10::1Answer
  4. D
    2001:db8:0:0:1::

Answer

The address '2001:db8::ac10::1' is syntactically invalid because it applies the double-colon (::) shortcut twice in a single address.
The IPv6 address '2001:db8::ac10::1' violates IPv6 syntax rules because the double colon (::) is present twice. Because '::' represents an indeterminate sequence of contiguous zero blocks needed to complete an 8-block (128-bit) structure, using it twice introduces structural ambiguity.

Step-by-Step Solution

1
Analyze the rules for IPv6 shorthand zero-compression.
IPv6 addresses consist of eight 16-bit hexadecimal blocks. Contiguous blocks of zeros can be omitted and replaced with a double colon (::).
Shorthand syntax reduces long IPv6 strings for human readability.
2
Evaluate the usage restriction of the double colon (::).
The double colon (::) shortcut may be used only ONCE within a single IPv6 address.
If used multiple times, it creates ambiguity regarding how many zero blocks belong to each double colon.
3
Examine each candidate address for syntax compliance.
'2001:db8::ac10::1' contains two instances of '::', making it impossible to determine whether it expands to 2001:0db8:0000:0000:ac10:0000:0000:0001 or 2001:0db8:0000:ac10:0000:0000:0000:0001.
Multiple double-colon references violate RFC 4291 IPv6 addressing architecture standard.

Key Concept

IPv6 Zero Compression Syntax Rules
Estimated Time:1m 30s
Rate this question

Topics

IPv6 Addressing Concepts and Header Structure

More questions from this topic