ipcalc-ng -r 24 | grep '255.255.255.0 = 24'
ipcalc-ng -r 29 | grep '255.255.255.248 = 29'
ipcalc-ng -r 30 | grep '255.255.255.252 = 30'
ipcalc-ng -r 255.255.255.0 | grep '255.255.255.0 = 24'
ipcalc-ng -r 255.255.255.248 | grep '255.255.255.248 = 29'
ipcalc-ng -r 255.255.255.252 | grep '255.255.255.252 = 30'