• classes A, B, and C include all the addresses which are valid to be assigned to hosts
  • what about 224.0.0.0 to 255.255.255.255?

Class D addresses

  • class D: reserved for IP multicast addresses
    • the four high order bits in a class D address are set to binary 1 1 1 0
    • not allocated to hosts
    • no default subnet mask
    • valid addresses range from 224.0.0.0 to 239.255.255.255

## Class E addresses

  • class E: experimental and reserved for future use
    • the four high order bits in a class D address are set to binary 1 1 1 1
    • not allocated to hosts
    • no default subnet mask
    • valid addresses range from 240.0.0.0 to 255.255.255.255
    • 255.255.255.255 is the broadcast address for this network

IP address class summary

Class First Octet default subnet mask (slash) default subnet mask (dotted decimal)
A 1 - 126 /8 255.0.0.0
B 128 - 191 /16 255.255.0.0
C 192 - 223 /24 255.255.255.0
D 224 - 239    
E 240 - 255