RFC 810 (rfc810) - Page 2 of 8

DoD Internet host table specification

RFC 810                                                     1 March 1982
                                                Host Table Specification
                                                                        
                                                                        
   3. If the first bit of the first octet of the address is 0 (zero),
   then the next 7 bits of the first octet indicate the network number
   (Class A Address).  If the first two bits are 1,0 (one,zero), then
   the next 14 bits define the net number (Class B Address).  If the
   first 3 bits are 1,1,0 (one,one,zero), then the next 21 bits define
   the net number (Class C Address) (RFC 796).

   This is depicted in the following diagram:

   +--------------+-----------------------------------------------+
   |0|  NET  |      LOCAL ADDRESS                      |
   +--------------+-----------------------------------------------+

   +---+--------------------------+-------------------------------+
   |1 0|       NET          |  LOCAL ADDRESS          |
   +---+--------------------------+-------------------------------+

   +-----+----------------------------------------+---------------+
   |1 1 0|           NET                    | LOCAL ADDRESS |
   +-----+----------------------------------------+---------------+

   4. The LOCAL ADDRESS portion of the internet address identifies a
   host within the network specified by the NET portion of the address.

   5. For the ARPANET (a Class A network), the NET address is 10
   (decimal) and the LOCAL ADDRESS maps as follows: the second octet
   defines the physical host, the third octet defines the logical host,
   and the fourth defines the IMP.

   +-+-------------+---------------+--------------+---------------+
   |0|     10      |    HOST       | LOGICAL HOST |      IMP      |
   +-+-------------+---------------+--------------+---------------+

   (NOTE:  RFC 796 describes the local address mappings for several
   other networks.)

   6.  It is the responsibility of the user using this host table to
   translate it into whatever format is needed for his or her purposes.

   7. Names and Addresses for DoD networks, gateways, and hosts will be
   negotiated and registered with the Network Information Center
   (NIC@SRI-NIC or (415) 859-4775) before being used and before traffic
   is passed by a DoD host.  For an interim period the NIC will attempt
   to keep similar information for non-DoD networks and hosts if this
   information is provided, and as long as it is needed, i.e., until
   intercommunicating network name servers are in place.

EXAMPLE OF NEW HOST TABLE FORMAT

   NET : 10.0.0.0 : ARPANET :