A very simple utility to work with CIDR ranges; it can list all IP addresses in a range or check if an address is part of a range.
To list all addresses in a range:
netmask 192.168.0.0/24
To check if an address is part of a range:
netmask 192.168.0.0/24 192.168.0.1
The exit code will be 0 if the address is part of the range and 1 if it isn't.