The other day I was installing a router and switch that needed to be trunked to a preexisting switch and a new firewall.
There were two T1 lines that needed to be routed before the VLAN's could be configured. Well the one T1 was not working and I had to trouble shoot what was going on. In doing so I created loopback plugs on the fly to test the ports for connectivity.
Loopback plugs are not only great for loopback tests, but they can save a little bit of time to see if a port is working without consoling in. That was one part of the trouble shooting was to see if the T1 module on the router was operational. I plugged in the loopback plug and the status was green. With the cable coming from the jack to the router it was red.
In the end it was an ISP issue. They inadvertently crossed the tip and ring set and it was an easy fix.
To make a T1 loopback plug do this:
Cut about 1 foot cord of twisted pair and strip off the casing that holds all the pairs together. Usually it's blue, grey, yellow or green. Untwist on paired color. I like to use the dark colors just so I can see where they are going in the RJ45 end.
Get a RJ45 end. The slots are numbered with the clip facing down towards your feet 1 - 8.
Insert one wire into slot 1 and the other wire into slot 2.
Insert slot 1's other end into slot 4 and slot 2's into slot 5 and terminate or crimp the end.
So the short description is 1 to 4 and 2 to 5 and you will have about 6 inches of wire hanging out. I put masking tape on these wires just for easy handling when removing it from the port. I would label it also for future use.
To make an Ethernet Loopback Plug do this:
Follow the exact same steps above. The only thing that changes is the pin count.
Place a wire end into slot 1 and another into slot 2.
Take slot 1's end and place it into slot 3 and take slot 2's and place it into slot 6.
So the pin count is 1 to 3 and 2 to 6. Crimp, tape and label.
Remember: A T1 loopback plug is for T1 ports it will not work with Ethernet ports and vice versa.
These are very easy to make and will save you a little bit of time and money in the long run.
J
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1 comment:
For your readers information, I have sometimes needed a loopback plug when I did not have the right one in my kit, or I needed to leave one in place for testing. In a pinch you can cut the end off a Cat 5 cable, strip the appropriate wires, twist the pairs together in the pattern above. Make sure that the bare twisted ends do not touch each other or the circuit will show a short, I just use a piece of tape to insulate them.
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