What a network diagram does
A network diagram is a visual map of your environment. It shows at least the devices and how they connect, eventually the details that make those connections meaningful. So if you make a network diagram, don’t make art, make it simple and clear.
If you’re stuck troubleshooting, stop and draw the network. Even a rough sketch can reveal what your brain was missing!
The Missing Piece: Interface Labels
The moment your diagram becomes truly useful is when you add interface labels. Because when you’re configuring the device later, you need to know which interface connects to which destination.
Designing With Failure in Mind
One of the tricky parts of building a diagram is that it forces you to think about failure before failure happens. So, you have to think about placing the hardware spread out, for example place one access point on one switch, and the other access point on the other switch. Now if one switch goes down, we don’t lose everything. This part of a diagram goes hand in hand with redundancy. For example, you draw to connection to a switch, one is my backup path.