What does a subnet mask tell you, and how many conventional usable host addresses are in a /26 IPv4 subnet?

The prefix length identifies the network portion of an IPv4 address. A /26 leaves six host bits, giving 64 total addresses. In a conventional multi-access subnet, one is the network address and one is the broadcast address, leaving 62 usable host addresses. For example, 192.0.2.0/26 spans .0 through .63, with .1 through .62 conventionally assignable. Special cases such as /31 point-to-point links use different rules. Provider-reserved addresses can further reduce availability, so distinguish mathematical subnet size from a cloud provider’s allocation policy.