Class A networks (0.x.x.x to 127.x.x.x) have an 8-bit network prefix with a 32-bit host number, and are also referred to as /8 networks.
The first bit is set to 0 to identify the network as a Class A type; this results in 128 (27) possible Class A networks, but those with prefix 0 and 127 are used for special functions and the upper half (with prefixes above 64) are reserved for future use.
This information was updated November 1999.
- 0 Internet Assigned Numbers Authority (IANA) (NET-RESERVED-1)
- 1 Internet Assigned Numbers Authority (IANA-ARIN) (NET-RESERVED-9)
- 2 Internet Assigned Numbers Authority (IANA) (NET-RESERVED-2)
- 3 General Electric Company, NJ (NET-GE-INTERNET)
- 4 BBN Planet, MA (NET-SATNET)
- 5 Internet Assigned Numbers Authority (IANA) (NET-RESERVED-5)
- 6 Army Information Systems Center - USAISC, Yuma Proving Ground, AZ (NET-YPG-NET)
- 7 Defense Information Systems Agency, VA (NET-DISANET2)
- 8 Bolt Beranek and Newman Inc., MA (NET-BBN-NET-TEMP)
- 9 IBM Corporation, NY (NET-IBM)
- 10 Internet Assigned Numbers Authority (IANA) (RESERVED-6)
This is reserved for private internet use, without connection to the global network
- 11 DoD Intel Information Systems, Defense Intelligence Agency, Washington DC (NET-DODIIS)
- 12 AT&T (NET-ATT)
- 13 Xerox Palo Alto Research Center, CA (NET-XEROX-NET)
- 14 Public Data Network, US (NET-PDN)
- 15 Hewlett-Packard Company, CA (NET-HP-INTERNET)
- 16 Digital Equipment Corporation (NET-DEC-INTERNET)
- 17 Apple Computer Inc., CA (NET-APPLE-WWNET)
- 18 Massachusetts Institute of Technology, MA (NET-MIT-TEMP)
- 19 Ford Motor Company, MI (NET-FINET)
- 20 Computer Sciences Corporation, VA (NET-CSC)
- 21 US Defense Information Systems Agency (DDN-RVN), VA (NET-DDN-RVN)
- 22 Defense Information Systems Agency, Washington DC (NET-DISNET)
- 23 IANA (reserved) (NET-DDN-TC-NET) (RESERVED-23)
- 24 US Cable Networks
- 25 Royal Signals and Radar Establishment, UK (NET-RSRE-EXP)
- 26 Defense Information Systems Agency, VA (NET-MILNET)
- 27 Internet Assigned Numbers Authority (IANA) (RESERVED-10)
- 28 ARPA DSI JPO, VA (NET-DSI-NORTH)
- 29 Defense Information Systems Agency, Washington DC (NET-MILX25-TEMP)
- 30 Defense Information Systems Agency, Washington DC (NET-ARPAX25-TEMP)
- 31 IANA (RESERVED-12)
- 32 IBM Global Services, NH (NETBLK-IBMGLOBALSERV)
- 33 DLA Systems Automation Center, OH (NET-DCMC)
- 34 Halliburton Company, TX (NET-HALLIBURTON)
- 35 MERIT Network Inc., MI (NET-MERIT)
- 36 Stanford University, CA (NET-SU-NET-TEMP)
- 37 Internet Assigned Numbers Authority (IANA) (RESERVED-37A)
- 38 Performance Systems International, VA (NET-PSINETA)
- 39 Internet Assigned Numbers Authority (IANA) (RESERVED-39A)
- 40 Eli Lilly and Company, IN (NET-LILLY-NET)
- 41 Internet Assigned Numbers Authority (RESERVED-41A)
- 42 Internet Assigned Numbers Authority (IANA) (RESERVED) (NET-RESERVED-42)
- 43 Japan Inet, Japan (NET-JAPAN-A)
- 44 Amateur Radio Digital Communications (NET-AMPRNET)
- 45 Interop Show Network, CA (NET-SHOWNETA)
- 46 Bolt Beranek and Newman Inc., MA (NET-BBNNET)
- 47 Bell-Northern Research, Canada (NET-BNR)
- 48 Prudential Securities Inc., NY (NET-PRUBACHE)
- 49 Joint Tactical Command, Control, and Communications Agency, AZ (NET-JITCNET1)
- 50 Joint Tactical Command, Control, and Communications Agency, AZ (NET-JITCNET2)
- 51 Department of Social Security of UK, England (NET-ITSANET)
- 52 E.I. duPont de Nemours and Co., Inc., DE (NET-DUPONT1)
- 53 cap debis ccs (Mercedes Benz), Germany (NET-DB-NET2)
- 54 Merck and Co., Inc., NJ (NET-MERCK2)
- 55 Army National Guard Bureau, VA (NET-RCAS2)
- 56 U.S. Postal Service, NC (NET-USPS1)
- 57 SITA - Societe Internationale de Telecommunications Aeronautiques, France (NET-SITA2)
- 58 Internet Assigned Numbers Authority (IANA) (RESERVED) (NET-RESERVED-58)
- 59 Internet Assigned Numbers Authority (IANA) (RESERVED) (NET-RESERVED-59)
- 60 Internet Assigned Numbers Authority (IANA) (RESERVED) (NET-RESERVED-60)
- 61 Asia Pacific Network Information Center (NETBLK-APNIC2)
- 62 European Regional Internet Registry/RIPE NCC (NETBLK-RIPE-C3)
- 63 InterNIC Registration (NETBLK-INTERNIC-2)
- 64 - 95 Internet Assigned Numbers Authority (IANA) (RESERVED-7)
- 96 - 126 Internet Assigned Numbers Authority (IANA) (RESERVED-8)
- 127 Internet Assigned Numbers Authority (IANA) (LOOPBACK)