My PC crashes/reboots my entire home router — 5 months, survived a router swap, need a permanent fix
My PC crashes/reboots my entire home router — 5 months, survived a router swap, need a permanent fix
TL;DR: My PC (not my PS5, not my phone, not anyone else's device) is somehow crash-rebooting my ISP's fiber ONT/router — full reboot, all LEDs off except power. It's been happening for 5 months, survived a full router replacement (different Huawei model), and survived removing the one software culprit I found (ExitLag's kernel driver, nfextlag.sys — ruled out with timestamps and a clean multi-day test). I've done extensive diagnostics myself (logs, PowerShell, event tracing) and I'm stuck.
THE SETUP
- ISP: STC fiber (Saudi Arabia)
- ONT/router: Huawei HG8245W5 → replaced ~2 weeks in with a Huawei HG8145X6-10. Problem continued on both.
- PC: Ryzen 9 9950X3D, RTX 5090, 64GB RAM, prebuilt by someone else (I did not build it myself)
- NIC: Realtek PCIe 2.5GbE (RTL8125 family), currently forced to 1.0 Gbps Full Duplex
- Wi-Fi card: Realtek 8922AE (separate known issue, logs an IOMMU DMA fault — probably unrelated but flagging it)
- OS: Windows 11
- Connected via Ethernet directly to the ONT
THE SYMPTOM
Not just "my PC loses internet." The entire household goes down. All router LEDs go dark except power. It comes back after ~30-45 seconds, then can crash again within minutes — sometimes looping for 1-2+ hours. Wi-Fi disappears from every device in the house during the event, confirming it's a full reboot, not just a WAN blip.
NEW: LED BEHAVIOR RIGHT BEFORE A CRASH
I watched the router's port lights closely during a live episode. Right before it reboots: the LAN port my PC is plugged into starts blinking extremely fast, and — critically — the WLAN light and even the TEL (phone/VoIP) light start blinking fast at the same time, despite having nothing to do with my PC. Shortly after, everything goes dark except power.
I've since ruled out two obvious explanations:
- Not a mesh/wiring loop: I unplugged my Wi-Fi mesh extender from the router entirely — problem still happened a few minutes later.
- Not a software/virtual network bridge on the PC: checked for Hyper-V/VMware/VirtualBox/ICS virtual adapters — none present.
This looks like my PC is sending a burst of broadcast/multicast traffic large enough to flood the entire router (all ports/radios see it, which is normal switch behavior for broadcasts) — and the router's firmware apparently can't handle the volume without crashing.
WHY I'M CONFIDENT IT'S THE PC
- Physically unplugging my PC's Ethernet cable during an active episode → failures stopped within ~10 minutes.
- Reconnecting the cable → router crashed again within ~5 minutes.
- PS4 and PS5 have used this same connection and cable for 10+ years, zero issues.
- Nobody else on the network has ever triggered this.
- Problem started the moment I got this PC (March), not before.
WHAT I'VE ALREADY RULED OUT (PLEASE DON'T SUGGEST THESE WITHOUT A NEW ANGLE)
- ExitLag's driver (nfextlag.sys): installed the same week problems started — huge red flag. Disabled it, uninstalled the app completely, verified zero trace left (`sc.exe`, registry, disk). Ran multiple clean test mornings under identical conditions (PC on all night, gaming, same router window) with zero outages logged. Felt solved for about a month. It came back anyway, unrelated to that app being present or absent.
- Router replacement (different Huawei model, same result)
- Mesh Wi-Fi extender unplugged entirely — no change
- Moving Ethernet port on the router
- Forcing 100 Mbps Full Duplex instead of Auto-negotiation (still crashed)
- Disabling Wake-on-LAN / Wake on Pattern Match
- EEE / Green Ethernet / Advanced EEE / Power Saving Mode — all already disabled
- No third-party network filter drivers or virtual/bridged adapters present
- Adapter error/discard counters are all zero — no obvious physical-layer errors
- No consistent time-of-day pattern anymore — it used to cluster ~6-8am, now happens at random times of day too
WHAT I HAVEN'T BEEN ABLE TO TEST YET
- Multimeter/ground-loop check between PC chassis and router (don't own one)
- Known-good *unshielded* cable swap
- USB-to-Ethernet adapter (bypassing the onboard Realtek NIC entirely)
- Full Linux live-USB boot test (isolating Windows from hardware)
- ONT in bridge mode behind a proper third-party router (haven't gotten STC to enable it yet)
- Packet capture at the exact moment of a crash to see what's actually flooding the router
- Professional/in-person diagnosis of the PC itself — I didn't build it, so I can't 100% vouch for the build quality, grounding, PSU, or motherboard
I'm not a networking pro — I've done my best with the diagnostics I know how to run, but I think this needs someone who's actually seen a case like this before. Happy to share PowerShell logs, event timestamps, and full history with anyone seriously trying to help. If that's you, I'm all ears.