What decides IP Address Class???

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What decides which class an IP Address belongs to...the IP Address number or the subnet mask?

@Shannon-Wright,

The subnet mask is what decides this and the classful addresses set forth by the IEEE.

The standard gave a range of IPs:
1.0.0.1 - 127.255.255.255 would have a default subnet mask of 255.0.0.0. Both would be converted to binary. This address class in binary would all begin with 01.

128.0.0.1-191.255.255.255 would have a default subnet mask of 255.255.0.0. Both would be converted to binary. This address class in binary would all begin with 10.

192.0.0.1-223.255.255.255 would have a default subnet mask of 255.255.255.0. Both would be converted to binary. This address class in binary would all begin with 110.

So try it.

1. Convert 126.0.0.1 to binary and note the first 2 binary digits.
2. Convert 180.0.0.1 to binary and note the first 2 binary digits.
3. Convert 222.0.0.1 to binary and note the first 3 binary digits.

Note how each conversion matched what I told you that the binary digits would be. This is how it worked for assigning classes. Then they applied the subnet masks to those division lines.

Thank you.