billion (2³²) addresses IPv4 made available. By 1998, the IETF had formalized the successor protocol, IPv6. This uses 128-bit addresses, yielding an address space of 2¹²⁸, 10³⁸, or 340 undecillion total addresses. Several transition mechanisms have been devised to allow IPv4 and IPv6 to interoperate, but IPv6 is not backwards-compatible with IPv4 and the two do not interoperate directly.

IPv6 provides other technical benefits