How many bits is an IPv6 address?

• A. 128
• B. 32
• C. 64
• D. 256

Answer: (A)

An IPv6 address is 128 bits long, which provides a vastly larger address space than IPv4’s 32-bit length. With 128 bits, there are 2^128 possible addresses (about 3.4×10^38), allowing enough unique addresses for every device and subnetwork for the foreseeable future. IPv6 addresses are typically written as eight groups of four hexadecimal digits (each group is 16 bits) separated by colons, and zeros can be compressed in practice for readability. The other lengths listed don’t match how IPv6 is defined, since 32 bits is the IPv4 size, 64 bits isn’t the standard address length for IPv6, and 256 bits would be larger than what IPv6 specifies.