GL-E750 slow VPN speeds (OpenVPN or WG)

Hello everybody! I am requesting your help with my Mudi GL-E750. I specifically bought it for the VPN feature, I host my own OpenVPN and WireGuard server and also bought a SurfShark subscription just for testing. The problem I am seeing is that no matter what I do the VPN are extremely slow when compared to my phone. For example on my phone on my OpenVPN server I am seeing around 20Mbps download and 6Mbps upload, while on my Mudi the max I am getting is 4Mbps both download and upload. The situation on WireGuard (which is supposed to be better) is even darker. I get around 0.5Mbps download and 5 Mbps upload, while on my phone it pretty much reaches my connection speed… around 40 Mbps download and 15 Mbps upload. Even on SurfShark the situation is not much better… I barely get 2 Mbps download while on my phone it gets to 60Mbps. I don’t know what to do since this is my primary use case. Is there a setting that could help?

i reached as high as 20mbps wireguard on the e750

Have you done any special configuration?

pretty standard, server is also a glinet router, configurations generated inside the UI

fibre internet at both server and client location

My server is running on a Windows machine (an Intel NUC) and also connected through fiber. The router is connected via 4G, but I have confirmed the connection itself is not the issue. Without going through the VPN I easily get 40-60Mbps download and over 30Mbps upload.

what is your mudi’s internet connection running on ?

and what did your handphone’s internet connection run on ?

My local telco limits my speed when it detects vpn connection

I am happy to report I have found the issue It seems the MTU value of the WireGuard client is 1420 which is not good for my servers connection type (IPv6 & PPoE… see here for details). Once I setup the value at 1280 the speed returned to normal.