ipv4 – How do you calculate the prefix, network, subnet, and host numbers? – Network Engineering Stack Exchange https://networkengineering.stackexchange.com/questions/7106/how-do-you-calculate-the-prefix-network-subnet-and-host-numbers
Learn IP Addressing and Subnetting – Connected Dots Networking http://www.connected-dots-networking.com/learn
Subnetting a Class C network address – TechRepublic https://www.techrepublic.com/article/subnetting-a-class-c-network-address/
CIPB – Decimal and Binary Conversion of IP Addresses https://www.countryipblocks.net/ip-address-conversion-to-decimal-and-binary-equivalents