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
The TCP/IP Guide - IP Subnetting Step #3: Determining The Custom Subnet Mask
How to calculate a subnet mask - Spiceworks
Q.86681: What subnet mask would accommodate this networ