Subnet Cheat Sheet – 24 Subnet Mask, 30, 26, 27, 29, and other IP Address CIDR Network References
What is a fixed-length subnet mask (FLSM)?
Subnet Mask - Network Encyclopedia
Subnet Mask Hexadecimal and Binary Conversion | VIAVI Solutions Inc.
Dan York on Twitter: "Nice cheat sheet for #IPv4 subnetting (and a good reminder that if you move to #IPv6 you don't have to worry as much about all these smaller subnets