What is the typical size of the subnet identifier in an IPv6 global unicast address?

In an IPv6 global unicast address, the subnet identifier is typically found in the third 16-bit block of the address. This structure is part of the overall breakdown of an IPv6 address, which consists of 128 bits total.

In a standard representation, the first 48 bits are reserved for the global routing prefix, which allows for the identification of the specific organization to which the address has been allocated. The next 16 bits are dedicated to the subnet identifier, which is meant to distinguish subnets within the organization. The final 64 bits are used for the interface identifier, typically created using the MAC address of the device or random numbers.

Therefore, in this context, the correct answer reflects the conventional sizing allocated for the subnet identifier, which is 16 bits. This structure facilitates efficient routing and proper address allocation within a given global prefix.