Sometimes, you will be given subnet masks (a range of IP addresses) to test, and in some cases, you will test only one single IP address. If you're using a subnet mask, then use the following table as a reference:
CIDR | Hosts | Net mask |
/30 | 2 | 255.255.255.252 |
/29 | 6 | 255.255.255.248 |
/28 | 14 | 255.255.255.240 |
/27 | 30 | 255.255.255.224 |
/26 | 62 | 255.255.255.192 |
/25 | 126 | 255.255.255.128 |
/24 | 254 | 255.255.255.0 |
/23 | 510 | 255.255.254.0 |
/22 | 1022 | 255.255.252.0 |
/21 | 2046 | 255.255.248.0 |
/20 | 4094 | 255.255.240.0 |
/19 | 8190 | 255.255.224.0 |
/18 | 16382 | 255.255.192.0 |
/17 | 32766 | 255.255.128.0 |
/16 | 65534 | 255.255.0.0 |