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Subnetting Tables and Tools

Subnetting can be ponderous. This post acts as a repository for subnetting information that is pertinent to certification exams and is important for the job. It contains subnetting tables for IPv4 class A, B, and C networks. It also has various links including two of my favorite subnetting calculators.

Watch my introductory lesson on subnetting here:


– Online IP Subnet Calculator: An excellent […] read more

Home Security Tips – Beyond the Security Alarm


A student of mine was concerned with potential break-ins and theft, and recently asked me about home-based wireless alarm systems and if they are secure. I told the student that anything can be compromised given some brains and perseverance. But with the right mindset, a wireless alarm can very well increase the security of a home. However, I like to think of an […] read more

Password checker programs and password strength.

Password checkers are great programs to use to find out just how complex your password is. Just a year ago (in 2010), a password such as |ocrian7 (which I show in my A+ Exam Cram 6th edition) was considered “strong”. Now, it’s considered to be “weak” in many password programs It’s an inevitable sign of the times. Password cracking programs and the computers that run […] read more

MACs, Hashes, and Digital Signatures

I often get this question from students: “What’s the difference between MAC, Hashes, and Digital Signatures?” So I thought I’d write a short article about it. For more about these topics, get my CompTIA Security+ Cert Guide today!

First let’s give a short description of each:

• Cryptographic hash functions: This is a procedure that calculates a fixed-size bit string (hash value) from a piece […] read more

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