How to determine the mask by IP address?

Question

Computer networks

For example, we have:
192.168.17.3
11000000.10101000.00010001.00000011
how to calculate which mask is needed? it is clear that class C, but why just put 255.255.255.0? or will it be different?
and if there are two subnets then why is the mask 255.255.254.0??? explain preferably in binary and decimal comparison or what?

Answer 1

There is no way to determine the mask from the IP address, since the IP address can belong to networks with different subnet masks.