Class A (1st Octet 1-127)Â Â Â -Â Â Â Â Â Network.Host.Host.Host
Class B (1st Octet 128-191) -Â Â Network.Network.Host.Host
Class CÂ (1st Octet 192-223)Â -Â Network.Network.Network.Host
Â
If the 1st Octet is:
1 – 127  Class A  Net.Host.Host.Host
128-192Â Class BÂ Â Net.Net.Host.Host
192-224Â Class CÂ Â Net.Net.Net.Host
224-240Â Class DÂ Â Multicast (Not used for host addressing.)
240-255Â Class EÂ Â Experimental (Not used for host addressing.)
 IP Addressing Rules
- Each Device (Host) Needs at Least One Unique IP Address
- All Devices on Same Physical Segment Share a Common Network ID(Subnet Mask)
- Each Physical Segment Has a Unique Network ID (Subnet Mask)