Several Class A, B, and C addresses are reserved for special purposes. You're probably familiar with most of these addresses.

  • 0.0.0.0 is a reserved host address.
  • Any address ending with 255 (e.g., the Class C address 222.34.56.255, the Class B address 145.23.255.255) represents the broadcast address for that class.
  • Organizations frequently use addresses in the range 10.0.0.0 to 10.255.255.255 for internal Class A networks.
  • 127.0.0.1 is the loopback/localhost address used for testing the internal stack. (The entire 127 range is reserved, although this is the only address for which a special purpose is specified.)
  • Organizations frequently use addresses in the range 172.16.0.0 to 172.31.255.25 for internal Class B networks.
  • Organizations frequently use addresses in the range 192.168.0.0 to 192.168.255.255 for internal Class C networks.