Unfortunately I can't help you with Proxmox but I suggest you to turn off one by one and to close possibilities what causes problem.

  @ComfySofa 

 

If you can connect the Zyxel switch in between, you can at least test whether there is some kind of incompatibility and therefore the transfer speed is bad.

Because at least I have a LAN-side incompatibility with a streaming box on my BE550 with the current final firmware, which seems to have been fixed by a BETA firmware at least for the last 3 days.

 

An adapter from another manufacturer, if it uses a different chipset, could of course also help as a test.

  @GrenSo 

 

I did have a tidy up of my networking cabinet last night....didnt have enough time to finish...... i flattened the proxmox box and tried again - no luck, so dropped back to the 1GB line which is working fine. I still have some more tidying up to do which i will do tonight when i get home.

 

I did assumed that this router is a current model....you stated "the final firmware" is it now out of production?

  @ComfySofa 

 

No, you misunderstood me. The BE550 is a relatively new router that I believe came onto the market in mid-2024.

By final firmware, I meant a new final firmware or official firmware, as opposed to a BETA firmware, since I am currently running the BE550 with a BETA firmware.

Ah - right...ok.

 

If it is hardware i hope they can fix this with a future firmware update....