Proper network address

Question

Which of the following are proper network (not host) addresses?

1. 192.168.23.0/24
2. 193.205.16.132/26
3. 172.16.4.0/20
4. 10.57.13.64/28

How can I tell? What is a proper network address?

Is a proper network address when the IP address is the same as the network address? For example in the first one that is the case.

Answer 1

I think proper here just means that the IP address in CIDR notation is the first address in the range specified by the IP address and its prefix.

This is the case for 192.168.23.0/24 and 10.57.13.64/28 and not the case for 193.205.16.132/26 (whose first address in the network range is 193.205.16.128) and 172.16.4.0/20 (whose first address is 172.16.0.0).