Subnet Mask Cheat Sheet - A Tutorial and Thorough Guide to Subnetting!
You are designing a subnet mask for the 172.26.0.0 network. You want 26 subnets with up to 1800 hosts on each subnet. What subnet mask should you use? - Quora
IP Subnetting Tool | IP Subnet Calculator Tutorial - ManageEngine OpUtils
Guide to Subnet Mask (Subnetting) & IP Subnet Calculator