ECN Forum Forums General Topics of the Trade Voice - Data - Video Discussion Cat5 2-jacks from one cable

You can get adapters that plug into the 8P8C (RJ45 for the non-pedantic) jacks which have two 8P8C jacks on them with the appropriate pairs split out. Using two of these adapters at both ends will allow you to run two ethernet connections over one cable.

Or you could make your own, using three 8P8C jacks.

This avoids the need to modify the permanently-installed wiring.

Usage of these types of adapters is commonly done, when the cost to run another cable is prohibitive. I've seen it done at two different, very large, companies.