These are one of the few topics that I constantly cover, review, bring up and explain. I've been doing this for over 30 years and still encounter layer-one issues.
Its a real shame since this is easy to prevent.
You can do one or all of the following:
buy a cable tester or network tool that can test a cable
if you have manageable switches, look at the current port status
if you have unmanageable switches, look at the port LED's since many of them will display the port speed, and possibly duplex.
lastly check the host connected to the switch, like your laptop, access point, etc, and see what speed or duplex it reports.
Since WIX cant embed youtube shorts, here is the link or click on the image
Here is the link to Netally, if you are interested in their products since we don't sell their products
