Nice feature – cable test on Junos EX switch

17 11 2011

There are some really nice features about EX switches, and I only just got round to giving this one a go.  You can run a port test – in the screenshots below it is ge-0/0/3 – and one of the tests run will tell you how far it is to the cable break.  This is a Time Domain Reflectometer (TDR) test.  In the example, it shows 17 metres to the break – so I can tell that there’s probably a cable from the port to the patch panel, but nothing plugged-in at the wall-port.

Browse to the web interface of the switch, log in and click the “Troubleshoot” tab along the top:








Hit the “Troubleshoot port” button and a wizard will start.  Select the port you are interested in:








The tests run are a link test, a cable test (the TDR one we are talking about here) and a configuration test:









And here’s our result – cable pair is open at 17 metres from the switch:



5 responses

5 01 2012
Dale Carpineti

This feature is not supported on the 4 port uplink module. I was looking forward to finally using this today and was immediately disappointed. When you start the test, only the built in ports are listed.

22 02 2012

Oh – that’s a shame – I didn’t know that. Thanks for the heads-up…

23 02 2012
Nick Kritsky

That’s a nice feature! Is it working on 10.4? Do you know if it can be done from CLI?

24 02 2012

Yeah – thanks for the idea – I just tried that and it works. I’ll post about it…

24 02 2012
TDR Cable Test on EX switches – CLI procedure… « The Data Plumber

[…] Cable Test on EX switches – CLI procedure… 24 02 2012 I recently wrote up my experience with a cable-test wizard in the JWeb interface, and was prompted to give it a go at […]

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