Which IPv6 prefix is used to embed IPv4 addresses within IPv6 addresses (IPv6 to IPv4 addresses)?

• A. 2002::/16
• B. 2001:0db8::32
• C. 224.0.0.0/4
• D. ff00::/8

Answer: (A)

Embedding an IPv4 address inside an IPv6 address is done using a special 6to4 mechanism. The prefix 2002::/16 is set aside exactly for this purpose, so IPv4 addresses can be carried in the IPv6 address itself. In practice, the 32-bit IPv4 address is written in hexadecimal and placed after the 2002 prefix, forming an address like 2002:c000:0204::/64 for the IPv4 address 192.0.2.4. This makes the IPv6 address recognizable as carrying an IPv4 endpoint and enables routing to the corresponding IPv4 reachability.

The other options don’t fit because they serve different purposes: 2001:0db8::/32 is a documentation/example prefix, not for embedding IPv4 addresses; 224.0.0.0/4 is the IPv4 multicast range; ff00::/8 is the IPv6 multicast range.