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Private IP address are addresses in the range of, -,, where the x in each octet can be a number ranging from 1 to 255. Addresses in these range are not routable on the Internet, thus it is known as private IPs.

IP addresses whether private or public are also masked using subnet masks, typically Class A, Class B and Class C.

Class A subnet are defined So for a IP address of with a mask of, the address range would be from - with only the first octet (the digits separated by the dot) staying consistent.

Class B subnet are defined as So it may range from - for an address of with mask of The first two octets are consistent.

Class C subnet are defined as and it is commonly used in smaller environment with less than 254 connected devices. Thus address with a mask of ranges from - It is also possible to use with a Class C subnet mask and it will have an address range of - with the three first octets being consistent.

Besides private IP addresses, there are also other reserved addresses not in use on the Internet. One is the loopback address which is, this just means pointing back to self.

Also within a subnet of IP addresses, the last IP is always the broadcast address thus it is not in use. Thus in the address range -, the last address is the broadcast address and is not useable by anyone. Packets sent to this address will be broadcast to every device within the subnet.

In Windows clients, Microsoft also automatically allocated IP addresses in the range of - to nodes that are unable to obtain IP address from a DHCP server.