I'm dealing with a frustrating network issue that's reproducible at several customer locations using KPN in the Netherlands. Here's what's happening:
Whenever certain PCs connect to the network, the entire internet becomes unstable or outright unusable for all devices, both wired and wireless. Strangely, these same PCs work perfectly fine on other ISPs.
I've ruled out client-side issues since the problem occurs regardless of the device used, with clean installations of Windows and different setups. It seems to be related to how the KPN modem behaves under load.
Here are the symptoms:
- When one PC connects, the internet drops for everyone.
- The local network may stay active, but WAN connectivity fails.
- Disconnecting the PC often restores the network after a brief wait.
I've tested various configurations including different network cards and had the modem in a DMZ with a separate router, but the issue persists. KPN won't allow a modem swap.
Has anyone else encountered similar problems with KPN or other ISPs where specific PCs cause network instability? Any ideas on modem firmware issues, escalation paths, or potential workarounds without switching ISPs?
4 Answers
Have you checked the network traffic between the problematic device and the router? It might help identify what's going wrong. I’d recommend using tools like Wireshark to analyze the traffic, even though the issue isn’t constant and typically occurs after a few minutes.
Trying to rule things out: Could it be that those PCs are involved in something nefarious, like a botnet? Make sure they aren’t consuming excessive bandwidth. Although you've replaced hardware, consider reinstalling the OS as a last resort.
What about switching out the KPN router for a different model? I know they allow using your own router on home connections. It could help resolve these issues you're facing.
Just to clarify, you've replaced everything on those computers except the motherboards, right? Do those boards share any similarities? Have you tried running Linux on those PCs to see if the issue still occurs?
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