XE75 Mesh suddenly capped at 94 Mbps - direct connect thru same cable exceeds 500 Mbps
Hoping someone has seen this issue before to save me disappearing further down this troubleshooting rabbit hole....
Setup
- Virgin Media hub in modem mode - 1 Gig Fibre
- Three TP-Link Deco XE75 units
- Virgin hub connected directly to the main Deco by one long Ethernet cable
- Other Decos connected through a mixture of Ethernet and wireless backhaul
- The system previously worked at much higher speeds
Problem
The whole Deco network now appears capped at approximately 92–94 Mbps. I’ve seen essentially the same ceiling on both a desktop via ethernet and phone over Wi-Fi.
My son initially noticed intermittent dropouts and buffering. I then realised some downloads had also been unusually slow.
The Deco app showed 94 Mbps down / 94 Mbps up under QoS “Total Bandwidth,” which initially looked like the obvious cause. However, changing the QoS settings hasn’t removed the cap.
What I’ve tested
- Disabled QoS completely: still approximately 94 Mbps up and down.
- Re-enabled QoS, removed all accelerated clients and changed Total Bandwidth to 1000/1000: still approximately 94 Mbps.
- Closed and reopened the app to confirm that the settings had persisted.
- Rebooted / restarted the 3 Decos: no change
- Reseated the Ethernet cable at both the Virgin hub and Deco ends, and moved the Virgin cable to a different Ethernet port on the main Deco: no change.
- Updated the firmware on all three Deco units: no change.
- Confirmed the Virgin hub is in modem mode.
- Connected a Windows laptop directly to the Virgin hub using the same hub port and Ethernet cable normally feeding the main Deco. After restarting the hub, the laptop achieved over 500 Mbps.
That last test seems to show that the Virgin connection, hub port and long cable are capable of well over 100 Mbps.
The repeatable 94 Mbps result looks very much like the Ethernet connection between the hub and main Deco is negotiating at 100 Mbps rather than 1 Gbps. The QoS figure may therefore have recorded the reduced link speed rather than caused it.
The Deco app was also behaving strangely at one point, showing zero connected clients and failing to execute a reboot - but restarting the main Deco restored live client and traffic information. The speed cap remained.
What next?
I'm just completely baffled by this now. Next I'll probably try making one of the other Decos the main unit and connecting it to the the same Virgin port / cable. Just wanted to see if anyone else had seen and solved this problem before I start messing with the mesh configuration and potentially lose the best part of my Sunday going round in circles...
Any help appreciated. 🙏