xls for IP Subnetting study and memorization
We all do it, and it is best to memorize the class 4 IP subnet’s.
Also this chart is very good to memorize and write out. If you know the block sizes and the /’s, you have 90% of what is needed.
Also this “Cheat sheet” has been around forever. Very good reference http://www.aelius.com/njh/subnet_sheet.html
Once you get the process down the “IP Subnet Calculator” makes a great reference http://www.subnet-calculator.com/