IP Addresses

The Host ID of 0 is always reserved to represent the network itself. The Host ID of 255 is reserved for broadcasts to all hosts on network. The iana Has a list of all Class A Blocks by company. 127.0.0.0-127.255.255.255 is reserved for Loopback (localhost).

Classful network

Class	1st 4 Bits	Network ID Range xyz for Host Octets	Network Bit Length	# of Networks	# of Hosts	Host ID Range wxy for Network Octets
A	0-------	001-126.x.y.z	8	126	16,777,214	w.1-254.1-254.1-254
B	10------	128-191.1-254.y.z	16	16,384	65,534	w.x.1-254.1-254
C	110-----	192-223.1-254.1-254.z	24	2,097,152	254	w.x.y.1-254
D	1110----	224-239.x.y.z			wiki
E	1111----	240-254.x.y.z

Subnetting

Supply the Subnet Mask OR CIDR (Classless InterDomain Routing) # and IP Address.

Network ID
Host ID
Hosts Allowed
IP Block Range Min
IP Block Range Max
Class
Default Subnet

Private Address Ranges

Use the following Private Address Ranges for use behined a Firewall, not on the public internet. They cannot be used on the public internet.

CIDR	Subnet Mask	Network ID Range xyz for Host Octets	Host ID Range y for Network Octets	IP Range
10.0.0.0/8	255.0.0.0	10.x.y.z	10.1-254.1-254.1-254	10.1.1.1 10.255.255.255
172.16.0.0/12	255.255.240.0	172.16.y.z	172.16.1-254.1-254	172.16.1.1 172.31.255.255
192.168.0.0/16	255.255.0.0	192.168.1-254.z	192.168.y.1-254	192.168.1.1 192.168.255.255