IP Subnetting Part 1 - IPv4

Despite the large number of jokes in high school about never needing to use mathematics after graduation, the art form known as IP Subnetting requires a solid grasp of math based on binary numbers (0, 1).  In this first part of my devoted attention on IP Subnetting, we'll focus on Internet Protocol version 4 (IPv4) addressing, some history, and the methods available to make IPv4 addressing go farther.

Understanding the "network" command

Many network engineers seem to misunderstand the use of the network command in routing protocols on Cisco IOS, especially once they see the usage in BGP.  This occurrence happens more frequently with those studying to become a CCNA, but may not be obvious to experienced engineers either.  Based on my own experience, I have very distinct memories of confusion when the concept I understood was first corrected by a more experienced engineer.  So let's breakdown the confusion.

Troubleshooting with OSI Model

At Layers 1-4, there are several tools or tricks available to quickly verify normal operations.  I have routinely used each of these tools for many years and expect many of them to be familiar.  Many of these tools are technology-specific, meaning that one tool has an application with one technology but not another.  I should also caution that the list below is not intended to be exhaustive or complete.  It's just a collection of my thoughts on what I find really useful.