@crrodriguez thank you again!

Thak you @crrodriguez! Now I'll have to read up on SFP DAC and AOC cable ... :-) I have to cover a distance of 50 meters using an existing Cat.6 cable: how about if I use one of the 8 RJ45 ports on...

Is there any way to use the SFP port with a copper RJ45 cable? Thanks for your help.

Thanks @d0ugmac1! Not a big deal in this case. I changed the ports more out of habit than out of real necessity ;-)

Ok ... after a factory reset and changing settings one by one, I can tell that the problem occurs when I change the port on which HTTP (8080) and HTTPS (4433) respond.

Thaks @Philbert but this was the first test I did