IPv6 Address Validation - Exam 200-125: Cisco Certified Network Associate Exam

Valid IPv6 Address

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Which IPv6 address is valid?



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A. B. C. D.


An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:).

An example of an IPv6 address is 2001:0db8:85a3:0000:0000:8a2e:0370:7334. The leading 0's in a group can be collapsed using ::, but this can only be done once in an IP address.

The correct answer is D. 2031:0:130F::9C0:876A:130B.

Explanation: IPv6 addresses are 128-bit long and are represented in hexadecimal notation. The notation uses eight groups of four hexadecimal digits, separated by colons (:).

Option A (2001:0db8:0000:130F:0000:0000:08GC:140B) is not valid because hexadecimal notation uses only the digits 0-9 and the letters A-F. The last group contains invalid characters 'G' and 'C'.

Option B (2001:0db8:0:130H::87C:140B) is not valid because 'H' is not a valid hexadecimal digit.

Option C (2031::130F::9C0:876A:130B) is not valid because it contains two consecutive colons (::), which is not allowed in IPv6 address notation.

Option D (2031:0:130F::9C0:876A:130B) is a valid IPv6 address because it has eight groups of four hexadecimal digits separated by colons. The two consecutive colons represent a group of consecutive zeros, and only one occurrence of consecutive colons is allowed in an IPv6 address.