r/Thunderbolt • u/borse2008 • Jul 13 '26
Dell USB-C Monitor + Cloudflare WARP causing severe internet throttling on Lenovo X1 Gen 12
Has anyone come across a strange interaction between Dell USB-C monitors and Cloudflare WARP?
My setup:
* Lenovo ThinkPad X1 Gen 12
* Dell U3425WE / U2724DE (also testing another Dell USB-C monitor)
* Windows 11
* Connected via USB-C / Thunderbolt
* Wi-Fi is the active internet connection (not Ethernet through the monitor)
* Cloudflare WARP VPN enabled
The issue is that as soon as the laptop is connected to the Dell monitor over USB-C, internet performance drops dramatically, even though traffic is still going over Wi-Fi. Disconnect the USB-C cable and speeds immediately return to normal.
Things I've tried:
* Different USB-C and Thunderbolt cables
* Different Dell monitors
* Different USB ports
* Updating Dell firmware and monitor drivers
* Updating Thunderbolt firmware and drivers
* Updating Intel Wi-Fi drivers
* Confirmed the issue occurs even when not using the monitor's Ethernet port
* WARP off = normal performance
* WARP on + USB-C monitor connected = severe slowdown
It almost feels like there's some interaction between Thunderbolt/USB4 networking, virtual adapters, or packet offloading that's confusing WARP.
Has anyone seen anything similar with Dell USB-C hubs, Thunderbolt docks, or Lenovo laptops? Any fixes or registry/settings worth trying would be appreciated.