A local business that I help out, called me and explains that they've had internet performance issues since day one.
They upgraded their internet service to fibre, then their local computer guy blamed the WIFI, so they put in a new WIFI mesh solution, now the same computer guy is blaming their switch. My friend is getting suspicious and asked if I had a few minutes to come by and check things out and give a second opinion.
Sometimes the best network troubleshooting lessons come from walking into a real network and discovering that things are not quite as organized as the network diagram suggested. In this case, a local business had been dealing with poor Internet performance for quite some time. They had upgraded to fibre, replaced their Wi-Fi system, and were now being told that the network switch was probably the problem. Before replacing another piece of equipment, I was asked to take a look. Within about ten minutes, a few classic network troubleshooting red flags started appearing.
The first problem was documentation—or more accurately, the complete lack of it. The office had three wiring closets, but nobody could clearly explain what connected to what or why all three closets existed. Cable labels didn't consistently match the faceplates or the cables at the patch panels, making it difficult to trace a connection from a workstation back to a switch. There was also no real testing methodology. Equipment was being purchased, installed, and replaced in the hope that something would eventually fix the problem. That can get expensive very quickly. Good network troubleshooting starts with understanding the environment before changing it.
Tracing the network uncovered a few more surprises. An old 10/100 hub was still being used, so it was replaced with a gigabit switch. More importantly, one of the connections back to the main switch was negotiating at only 100 Mbps instead of 1 Gbps. That does not automatically prove that the cable is bad, but it is certainly a reason to investigate the physical layer. A damaged cable, poor termination, incorrect wiring, or another cabling problem can prevent a gigabit Ethernet link from negotiating properly. Continuing the investigation uncovered another old hub and several examples of improvised cabling, including network cable spliced into older telephone wiring.
This was a good reminder that replacing switches, access points, or Internet services is not a substitute for basic network troubleshooting. Before blaming the ISP, Wi-Fi, switch configuration, or application, take a step back and verify the physical network. Trace the cables, check link speeds, inspect terminations, test questionable runs, and label everything so the next person does not have to solve the same mystery. Sometimes the problem really is complicated, but sometimes the answer is hiding in a wiring closet—and occasionally that answer involves a cable splice that makes you wonder what happened five years ago. The original visit was a great example of why Layer 1 troubleshooting, documentation, and a repeatable testing methodology should still be part of every network technician's toolbox.
