Learn To Make Your Own Loopback Adapter

Making sure you have testing equipment on hand for any install jobs is a must. However, sometimes equipment is forgotten or lost, and exceptions must be made. Making your own loopback adapter can be a fun exercise to learn the basics of how an ethernet connection works or if you have the tools available and want to save $6. Whatever your reasons are for making a loopback adapter we’ll walk you through the entire process with this guide.

First things first you’ll need to gather the following equipment:

A small length of ethernet cable. Less than one foot is preferred.

One RJ45 connector. We recommend using one with load bars. These load bars will make the terminating process extremely easy.

A crimp tool, a stripping tool, and a pair of precision cutters.

A switch for testing.


Step one: Strip the cable

To build this loopback adapter we’re going to need to use the conductors that are inside ethernet cabling. Accessing the conductors is a simple process. Simply strip away part of the jacket. This can be an inch or two at the end of the cable or right in the middle. Once the incision is made pull away the jacket and then pull out all the conductors.

You’ll be left with 4 pairs of wires. These are the conductors that make up all patch cables. Set aside three of the pairs. Keep one pair ready for termination. We’ll be using the white & orange pair.


Step Two: Line up the conductors

A standard ethernet connection uses 4 pins to complete the connection. Pins 1 & 2 are used for sending while pins 3 & 6 are used for receiving. To set up this loopback adapter we’ll have to connect pins 1 & 3 and then 2 & 6. Trim the wires down to around 6 inches. Untwist both ends of the pairs a little bit to allow the wires to be lined up. Set the first white conductor and the first orange conductor next to each other. Then add the second white conductor next. Lastly comes the second orange conductor. You’ll have to leave enough space between this conductor and the second white conductor.


Step Three: Termination time

Now it’s time to insert these conductors into the load bar and terminate the connector. Keeping the wires lined up, slowly insert them into the load bar. Making sure the wires stay in the correct order may be slightly difficult. Once they are in the correct position push the load bar down onto the wires as far as it can go. Trim any excess wire. Insert the load bar into the connector. Use your crimp tool to crimp the RJ45 connector.


Step Four: Testing

Let’s test this thing out. Grab your switch and plug in your new loopback adapter into one of the ports. The connectivity light on the corresponding port should light up indicating a proper connection. If it does not light up check your pinout and make sure the wires are in the correct position.


Building your own loopback adapters can end up being more expensive than just buying one outright if you don’t have the equipment on hand already. However, if you have some spare parts laying around, making your own loopback adapter can be a fun, cheap way to test out networking equipment.