Can anyone confirm or enlighten me about the minimum length of cat 5, cat 5e, and cat 6 cables before performance degrades?

Hi all

This has been my questions in a while. When I was doing network installation for a customer using HP Gigabit switches without POE, I tried to make short patch cords to make cable management looks great.

I ended up having all sorts of problems and then I just replace them all with 1m to 2m patch cords and all the issue was gone.

Then I saw some r/homelabs posts of people using very short patch cord to connect patch panel to switches and they said they experience no perfornance degradation nor any problem of intermittent drops.

Today, I am compelled to redo short patch cords again. I made 22cm patch cords and 15 cm patch cords. When I installed the 22cm cables, the switch shows gigabit lights turns on, until I plug in the 15cm cables, the swotch only shows 10/100 mbps light. I exchange the 15cm cable with regular 1m cable and the connection goes to 1gbps. Then I tested with the 22cm cables, the switch still manage to go to 1gbps. Only when I plug the 15cm cables, the switch only recognize 10/100.

I tested file transfer with both 1m and 22cm cables and both can run up to 105MBps (Mega BYTES) for file transfer between PC. i did not test the 15cm since the switch cannot recognize its full potential.

At my lab, we use TP-Link TL-SG1024 which is 24 port gigabit switch. For the cables, I used Schneider Digilink cat 6 cable.

Can someone confirm me what is the shortest patch cord cables I can make before performance degradation?