Troubleshooting Old School
I was in town running some errands when this local business calls me and asks if I can help out. Something is going on within his network and some of the VOIP phones are not coming online. It has been 2 days and the IT support company that usually supports him has not answered any of his calls or emails.
He said that he didn't want to ask me earlier because he only thought I worked on huge complicated networks and was 'beneath me'. I chuckled and told him a large network is basically the same as a small network, just more of the same stuff duplicated. I explained that it doesn't matter to me how many devices are on them, troubleshooting methodology is pretty well the same.
I have never worked on this network, nor do they have any documentation - yeah real shocker. Of course, I don't drive around with my laptop, cable tester, and tools, so I started troubleshooting 'old school'.
I took a VoIP phone that didn't work and moved it to the closet where the VOIP gateway was located and plugged it in. Odd, it seems like it couldn't get an IP address or register with the gateway.
I disconnected all the wires from the switch that was HANGING by its ethernet cables (something else to fix) and only left the VoIP gateways connected. Bingo, the phone was online.
Then I simply plugged the cables back in, one by one, and tested all 10 phones to be certain they all worked until I found the suspect cable. When I asked where the mystery cable went, he said "That's the telecom cabinet, the IT support company has that key".
I then asked if he knew of anything in the telecom closet that required network connectivity like an IoT device, camera, or alarm system or if there was any cabling in the office that terminated there. he replied, "Pretty sure there isn't".
We left the mystery cable unplugged, he put a call into the IT service company that has a key to that room and we checked everything that requires network connectivity and all worked well.
Hope he figures out what is in that telecom closet ;) Regardless who provides support, you have access to all rooms on your premesis. And please "DOCUMENT AND LABEL!!!"