Which statement correctly describes IPv4 and IPv6 addressing in terms of address length and space?

• A. IPv4 uses 32-bit addresses with about 4.3 billion addresses; IPv6 uses 128-bit addresses.
• B. IPv4 uses 64-bit addresses; IPv6 uses 96-bit addresses.
• C. IPv4 uses 128-bit addresses; IPv6 uses 32-bit addresses.
• D. IPv4 and IPv6 both use 256-bit addresses.

Answer: (A)

Understanding how many addresses a protocol can support comes from the length of its addresses. IPv4 uses 32-bit addresses, which gives 2^32 possibilities—about 4.3 billion unique addresses. IPv6 expands this drastically with 128-bit addresses, yielding 2^128 possibilities, an astronomically larger pool. This combination—IPv4 at 32 bits and IPv6 at 128 bits—accurately describes both the length and the resulting address space. The other statements misstate the lengths or reverse them (for example, 64-bit or 96-bit for the other protocol, or 128-bit for IPv4 and 32-bit for IPv6), or claim both use 256-bit addresses, which isn’t correct.