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Networking basics - Private IP Address

Private IP addresses are not valid on the Internet whereas, public IP addresses are valid as nodes on the Internet. They can be resolved and routed across the Internet from one point to another unlike private IP.

The following IPv4 address ranges are reserved for private networks:

Class A network:

10.0.0.0 - 10.255.255.255

(10/8 prefix) range

Used for large network that requires a bigger pool of 16 million private IP addresses

Class B network:

172.16.0.0 - 172.31.255.255

(172.16/12 prefix) range

Used for medium-sized network that requires 65000 private IP addresses

Class C network:

192.168.0.0 - 192.168.255.255

(192.168/16 prefix) range

Generally used for IP range on smaller network for easier addressing of 254 IP addresses.

Note: 169.254.0.0 range is allocated to client when they fail to obtain address from a DHCP server.

Refer to RFC 1918 for a complete description for Private IP addresses

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‎09-24-2009 12:24 AM
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The range 169.254.0.0-169.254.255.255 has been reserved by the Internet Assigned Numbers Authority (IANA).

It is used for what is called Automatic Private IP Addressing (APIPA), and are also not routeable on the Internet.