Para calcular una subred:
http://jodies.de/ipcalc?host=192.168.0.1&mask1=24&mask2=

^ IPs   ^ Clase  ^ Máscara         ^
|16777214| /8 | 255.0.0.0     |
|  65534| /16 | 255.255.0.0     |
|    254| /24 | 255.255.255.0   |
|     30| /27 | 255.255.255.224 |
|      1| /32 | 255.255.255.255 |