Comment by nullc

Tapping is even easier if you have access to the cable end in a patch panel.

I have a computer setup with a one-way gige connection for reviewing potentially malicious content in an air-gapped manner. The transmit side transceiver needs to see an incoming signal, so I just use one of these to feed its own output back into it:

https://www.amazon.com/dp/B0B8ZHBK26