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
255.255.255.240 Subnet
Subnet Mask Reference Table | Brain Knowledge
Subnet Mask Cheat Sheet - NetworkCalc
Useful subnetting cheat sheet. This will help when subnetting. ┃ Securitron Linux blog.