What happens if you use a two pair ethernet cable between two 10GbE capable devices?

SIlly topic. Will they negotiate to 100Mbit or is there a chance that they will negotiate to 1Gb?

I don’t see how they could negotiate 1gig with only half the connection present. There’s probably a balun or something that lets you try and cram a 1ghz differential signal across only four wires, but it’s probably cheaper to redo the run.

Nope. 1Gbps requires 4 pairs


You can get gigabit over a single pair but its not used in computing AFAIK. You’d need 4 pairs to negotiate gigabit.