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Private IP Addressing

Public IP addresses are addresses that are valid as nodes on the Internet.

They can be resolved and routed across the Internet from one point to another.

Unlike public IP, private IP addresses are not valid on the Internet.

Three range of private IP addresses has been selected for the three network class.

For Class A network, 10.0.0.0 - 10.255.255.255 (10/8 prefix) range (For big network that requires a huge pool of 16 million private IP addresses)

For Class B network, 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) range (For medium-sized network that requires 65000 private IP addresses)

For Class C network, 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) range (Commonly used IP range on smaller network for easier addressing of 254 IP addresses. May not necessarily be smaller network but network managed in smaller blocks.)

Beside these, there is Microsoft's 169.254.0.0 range of default IP addresses that are allocated to systems when they are unable to obtain address from a DHCP server.

Having a private IP address on the Internet has no value even if sole purpose of the node is for sending UDP traffics, which requires no acknowledgement, as most properly configured routers will drop packets with a source/destination private IP addresses.

Similarly, having public IP addresses behind a NAT router will not affect your network operation since the addresses are translated to the WAN side IP before being forwarded to the Internet, with exception to accessing of the block of public addresses you are using behind the NAT.