How to find that an IP address is a LAN IP or WAN IP?

StackOverflow https://stackoverflow.com/questions/10311501

  •  03-06-2021
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Question

How can I find that an IP address is a LAN IP address or WAN IP address? I am writing a C API in Windows.Thanks

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Solution

Private IP addresses are usually set from the private IP address spaces:

  • 10.0.0.0/8
  • 172.16.0.0/12
  • 192.168.0.0/16

If the interface's IP addresses falls into one of these spaces, you can assume it is a private IP. Otherwise, it is a public (WAN) IP.

OTHER TIPS

Most likely, what you want to determine is whether the address is a global address, or a private address. The wikipedia article lists the address blocks that are reserved for private use.

LAN vs WAN is meaningless in TCP/IP. There are only netmasks. If you can define what you mean by a LAN in terms of an IP netmask, the problem is trivial: does the IP address and the netmask give a non-zero result. If you can't define that, there is no solution.

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