Troubleshoot cable runs from your desk amongst TDR!
An oftentimes overlooked characteristic inwards a lot of switches is TDR (Time Domain Reflectometry). If you lot don't know virtually this characteristic already, larn create to salvage a lot of fourth dimension together with coin when troubleshooting your copper access ports.
WARNING: Running these diagnostics volition drive you lot to lose connectivity on the interface during the testing period. I ran approximately elementary tests on an EX4200 together with precisely ran a ping -t to a server from my windows machine. I lost vi packets – but I was also connected through an IP phone. Your results could vary. If you're going to play amongst the command, produce it inwards a essay environs or at to the lowest degree on a essay port. If you're doing it to expect into a production problem, know that the ascendence is intrusive together with human activity accordingly.
What is TDR?
Put simply, TDR diagnostics on your switch tin flaming say you lot virtually issues amongst your copper cables, whether they endure wire breaks or otherwise. Your switch does this yesteryear sending pulse onto the wire together with thence taking measurements on whatever percentage of the betoken that is reflected dorsum to the transmitting interface. Reflections would endure caused yesteryear whatever discontinuity inwards the wire, including wire breaks or other issues.
If you're a network guy, that's every bit much every bit you lot postulate to know virtually the underlying technology. If you lot desire to know more:
http://en.wikipedia.org/wiki/Time-domain_reflectometer
All EX switches back upward this characteristic for copper ports. The fiber/optical equivalent would endure OTDR (Optical Time-domain Reflectometry). If you lot desire to produce OTDR, you'll postulate to larn your Fluke out.
Why produce you lot postulate it?
I promise that quite a few obvious answers to this query convey already come upward to your mind. Aside from non having larn your tools out together with exit your desk, my favorite matter virtually TDR is that I don't convey to schedule together with pay for a cabling contractor to view a remote branch constituent to cheque if maybe at that spot mightiness endure an number amongst the cable perchance – because at that spot commonly never is.
How to role it
The commands are simple:
request diagnostics tdr showtime interface <interface-name>
show diagnostics tdr interface <interface-name>
Those are actually the exclusively commands you'll postulate to know, but you lot tin flaming supercede "start" amongst "abort" if you lot desire to cancel the test. The initial "show" ascendence volition present that the essay has started together with the eventual output looks similar what I pasted below. In this example, I plugged a twenty pes cable into the port together with ran the essay amongst nix on the other end, that's why you lot come across open.
root@Test-Sw> present diagnostics tdr interface ge-0/0/0
Interface TDR detail:
Interface name : ge-0/0/0
Test status : Passed
Link status : Down
MDI pair : 1-2
Cable status : Open
Distance fault : vii Meters
Polartiy swap : N/A
Skew time : N/A
MDI pair : 3-6
Cable status : Open
Distance fault : vii Meters
Polartiy swap : N/A
Skew time : N/A
MDI pair : 4-5
Cable status : Open
Distance fault : vi Meters
Polartiy swap : N/A
Skew time : N/A
MDI pair : 7-8
Cable status : Open
Distance fault : vii Meters
Polartiy swap : N/A
Skew time : N/A
Channel pair : 1
Pair swap : N/A
Channel pair : 2
Pair swap : N/A
Downshift : N/A
Then nosotros convey a skillful one:
root@Test-Sw> present diagnostics tdr interface ge-8/0/16
Interface TDR detail:
Interface name : ge-8/0/16
Test status : Passed
Link status : UP
MDI pair : 1-2
Cable status : Normal
Distance fault : 0 Meters
Polartiy swap : Normal
Skew time : 48 ns
MDI pair : 3-6
Cable status : Normal
Distance fault : 0 Meters
Polartiy swap : Normal
Skew time : 0 ns
MDI pair : 4-5
Cable status : Normal
Distance fault : 0 Meters
Polartiy swap : Normal
Skew time : xl ns
MDI pair : 7-8
Cable status : Normal
Distance fault : 0 Meters
Polartiy swap : Normal
Skew time : 48 ns
Channel pair : 1
Pair swap : MDI
Channel pair : 2
Pair swap : MDI
Downshift : No Downshift
Notice – 0 Meters isn't the cable length, but the length at which the error is estimated. This ascendence doesn't stair out your cable run for you. If the cable condition is normal together with you lot come across 0 meters, you're good. If at that spot is another status, you lot may withal come across 0 meters. If you lot run the essay on an empty port, you lot could come across 0 or 1 meters depending on the yoke since the calculations aren't exact.
There are diverse statuses other than "good" or "open" you lot mightiness larn dorsum on a yoke amongst this command. More data on the ascendence together with all of the output fields tin flaming endure industrial plant life here:
