IP Version Numbers 2021-01-28 In the Internet Protocol (IP) there is a field to identify the version of the internetwork general protocol. This field is 4 bits in size. Standards Action 0-1 Reserved 2-3 Unassigned 4 IP Internet Protocol 5 Reserved (Historic) Moving IP versions 5, 8, and 9 to Historic 6 IPv6 Internet Protocol version 6 7 Reserved (Historic) 8 Reserved (Historic) Moving IP versions 5, 8, and 9 to Historic 9 Reserved (Historic) Moving IP versions 5, 8, and 9 to Historic 10-14 Unassigned 15 Reserved Jon Postel mailto:postel&isi.edu