read-only ethernet cable

Hello, I'd like to make a read-only ethernet cable to sniff traffic to send it to snort. I found a lot of links on the web but some has lack of information other are to complex. I found [this](https://www.instructables.com/Read-only-Ethernet-monitor-cable/) but it seems to me that it speak about a read-only one-way cable. Obviously I need a twa-way cable. Can you help me to find a simple how to ?
thanks

cable computerforensics ethernet