Xodium's Adventures in Business Networking: The Fix

At the end of 2025, I wrote a big post about how I was just...flummoxed trying to get a client's business network up and running and to get some IoT equipment they were using up and running too. 

 

This finally came somewhat to a head today, and I'm pleased to report I finally--with the help of a suggestion from a friend--figured it out.

 

Said friend had a suggestion to give Wireshark a try, to see if I could spot any rogue DHCP servers on the network. I kept this in mind for a time when I could go back to do more troubleshooting, and that day finally came. A weekend where no one would be using any of the network, so I could pull the whole thing offline and do whatever I wanted. 

 

I went in fully expecting to rip the whole thing asunder and do it all over. After all, this was someone else's mess I was cleaning up, and I had no idea what was going on or why certain things were set the way they were. But then I remembered the Wireshark tip. I installed it on my laptop, ready to bust it out...but then I had a moment of clarity: They have a Windows Server instance they're no longer using, but it's still connected to the network. Can Windows Server be set up to do DHCP?

 

The answer? A resounding yes it sure can. Because the minute I unplugged that server (that again, was no longer being actively used, it was for their old recordkeeping system that they've since transitioned away from), things began resolving properly. I set one of the machines back to auto IP rather than being manually assigned. It worked without issue. I did the same to another machine. Same thing happened. 

 

I did a quick ping test in command prompt. Things were now routing to the proper gateway, as they should. No packet loss. Everything was working. I can't believe it. 

 

I decided to go further and route the Connection Pro back in, and connected all the wired clients to the Connection Pro. It took a bit for everything to DHCP properly, but it did, and everything worked as it should. Consider this my mea culpa, Connection Pro. I'm sorry I blamed you.

 

To finally, decisively put the nail in this coffin, I go to the back to check that IoT equipment that was previously giving me all the trouble. I had it run a connection test. BAM. Green across the board, now able to reach all of the servers it needed to reach.

 

I couldn't believe it. I was punked by a rogue DHCP server.

 

If I had to guess, this was set up as such because all of the previous clients needed to connect to this central server for their record keeping, and for some reason the previous tech decided to make it the DHCP server/router when they had AT&T service. So when Comcast came in to install their service, all that went right out the window and chaos ensued.

 

Now, obviously, this means they can't use that server anymore in its current state. I'd like to go back, log into the server, and kill whatever service is allowing it to act as a DHCP server, and put it back on the network just in case my client needs to access it for any reason. But given they seem perfectly happy and have transitioned everything to their new system, I don't think I'm in any rush to fix that. Definitely a later me problem, for sure.

 

Now, if you'll excuse me, I've got a vintage computing convention to prepare for because boy time goes by fast.