Classful Addressing

• Originally, all IP addresses were divided into five distinct “classes”

• Class A

• • First bit is 0, range of first octet: 0-127

• Class B

• • First bits are 10, range of first octet: 128-191

• Class C

• • First bits are 110, range of first octet: 192-223

• Class D

• • First bits are 1110, range of first octet: 224-239, used for multicast

• Class E

• • First bits are 1111, range of first octet: 240-255
  • Reserved: packets with class E addresses are called “Martians”