In order to make sure that now two devices share the same public IP, addresses need to be parcelled out.

  • IANA parcels out IP addresses in contiguous chunks called network blocks.

      First Decimal Value Addresses Hosts per Network Id
    Class A 1 - 126 1.0.0.0 - 126.255.255.255 16,277.214
    Class B 128 - 191 128.0.0.0 - 191.255.255.255.255 65,534
    Class C 192 - 223 192.0.0.0 - 223.255.255.255.255 254
    Class D 224 - 239 224.0.0.0 - 239.255.255.255.255 Multicast
    Class E 240 - 254 240.0.0.0 - 254.255.255.255.255 Experimental

  • Class A: Always begins with 0xxxxxxx

  • Class B: Always begins with 10xxxxxx
  • Class C: Always begins with 110xxxxx
  • Class D: Always begins with 1110xxxx
  • Class E: Always begins with 1111xxxx

IANA#

ARIN#

CIDR#

Subnetting#