A repository of helpful tools selected to aide students learning how to subnet...

Tutorials, Workshops, and Articles:
Easy Subnetting (.pdf)
Adapted from an article originally published on the Internet by Greg Stanley, MCP; rewritten by Beau Sanders; this article is written to help students who need a system to answer subnetting questions for certification exams or college networking courses, where calculators and/or tip sheets are not allowed; the writer assumes that the reader is familiar with subnetting theory and knows how to count in binary at least to 16 bits. This article was last revised on November 4, 2018.
Seven Steps to Subnetting (.pdf)
Excerpt from MCSE Guide to Microsoft® Windows 2000® Networking Certification Edition, written by Kelly Caudle, Walter J. Glenn, and James Michael Stewart; published by Course Technology; Errata: This article was written prior to the change allowing the first and last subnets in an incremental range to be used. This document was revised on November 4, 2108 to reflect the change allowing the first and last subnets in an incremental range to be used.
Subnet Workshop Worksheet (.pdf)
Blank Subnet Worksheet used in our Subnetting Workshop (.pdf)
IP Subnetting, Variable Subnetting, and CIDR (Supernetting)
Excellent article on subnetting
IP Variable Length Subnet Masking (VLSM)
Learn how to subnet a subnet and better manage address space when networks have varying number of host requirements 
Subnetting Web Sites:
Free account available. Site offers Pro account for a small fee. Subnetting.net is full of free tools designed to help you learn and master subnetting. Check out the Video and Written Tutorials, Practice Questions, and the Subnetting Game to hone your skills. If you're studying for the CCENT or CCNA exam, the Pro Account provides many additional features including CCENT/CCNA Videos, Labs, and Practice Questions.

An excellent online resource for all things related to subnetting; includes several excellent subnet calculators

Subnet Calculators and Tip Sheets:
Solarwinds.net Free Advanced Subnet Calculator
One of the best free subnet calculators found on the Internet; click on the "Download Adv Subnet Calculator Now", complete the contact form, and follow the online instructions

Subnetting Tip Sheet (.pdf)
A homemade CCNA tip/cheatsheet that collects the most important subnet details on one page; revised November 4, 2018

Subnetting Tips from EasySubnetting.com (.pdf)
Charts and tips to help subnetting students focus on the fundamentals and binary math; posted November 5, 2018