IPv6 address rules: Which combination of statements about IPv6 addressing is correct?
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A1 and 3
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B2 and 4
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C1, 3 and 4
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DAll of the above
Answer
Correct Answer: 2 and 4
Explanation
Introduction / Context:IPv6 textual representation includes several rules that reduce address length while preserving unambiguous interpretation. Knowing which statements are valid ensures accurate configuration and troubleshooting.
Given Data / Assumptions:
- (1) Leading zeros are required.
- (2) Two colons (::) are used to represent successive hexadecimal fields of zeros.
- (3) Two colons (::) are used to separate fields.
- (4) A single interface will often have multiple IPv6 addresses of different types.
Concept / Approach:
Correct rules: Leading zeros are optional, not required. Double-colon (::) denotes one contiguous run of zero 16-bit blocks and may appear only once in an address. Field separation uses single colons. Interfaces typically hold multiple addresses (link-local, global unicast, possibly unique-local, and temporary/privacy addresses).
Step-by-Step Solution:
Reject (1): leading zeros are optional and may be suppressed.Accept (2): :: compresses one sequence of zero blocks.Reject (3): single colon separates hextets; :: is not a separator.Accept (4): multiple addresses on one interface are normal in IPv6.Verification / Alternative check:
Examples: 2001:db8:0:0:0:0:0:1 can be 2001:db8::1; 2001:db8:1:0:0:0:0:abcd becomes 2001:db8:1::abcd. Devices show both link-local and global unicast on the same interface with show commands.
Why Other Options Are Wrong:
Any choice including (1) or (3) conflicts with IPv6 textual rules.
Common Pitfalls:
Using :: more than once; forgetting that :: can represent different counts of zeros depending on the rest of the address; assuming each interface has only one address as in traditional IPv4.
Final Answer:
2 and 4