Question 80
A router interface has IPv6 address 2001:db8:0102:0022::52/64. Which network prefix correctly represents the directly connected IPv6 /64, with host interface-ID bits excluded?
Explanation
Correct Answer
With an IPv6 /64, the first four 16-bit hextets form the network prefix and the final 64 bits are the interface identifier. Clearing those interface-ID bits in 2001:db8:0102:0022::52 produces 2001:db8:0102:0022::/64. That address represents this connected subnet; it is not the individual host address or a prefix from a neighboring /64.
Incorrect Answers
2001:db8:0102:0023::/64 changes the fourth hextet, which is inside the /64 network portion of 2001:db8:0102:0022::52. It describes a neighboring IPv6 subnet rather than the connected prefix of the indicated interface.
2001:db8:0102:0022:1::/80 is an /80 representation, a different prefix length and network boundary from the given /64. The question requires the connected /64 exactly rather than an arbitrary narrower range within it.
2001:db8:0103:0022::/64 changes the third hextet, also part of the fixed /64 network identifier. IPv6 network matching cannot discard that difference simply because both addresses start with the documentation prefix 2001:db8.