Diagnosing cabling problems

[dhnl]

We've run into this situation numerous times.

Customer reports typical cabling related network/computer problems. Dropped network connections, slow transfer of data, general system flakiness.

We arrive on site and confirm problems. Replace patch cables, problems persist. Test horizontal channel with Omniscanner 2 or DSP 4300. CAT5e test passes perfectly. Test horizontal link including patch cables. Test passes perfectly. Tear out existing horizontal cabling and replace. All problems vanish.

Is there a different piece of test equipment we should be using in addition to our certification tools? Any other suggestions for methods of proving cabling faults even when the certification test passes?

The same also applies where a physical inspection of the cabling shows obvious violations (crushed by tiestraps/electrical staples, strapped to AC circuits, tight bends, kinks). Irregardless of such the certification test still passes. This leaves us with little ammunition to use when recommending complete replacement.

 

[DTSMAN]

I have been through this before. I have had cable issues cause network issues that were certified. Do a visual inspection and replace and or move those that are not ran properly. This disscussion has been here once before. I took a certification tester and tried to emmulate field issues in house to show techs what to look for. The tester passed cables I had rolled around neon signs, flourescent lights and even cut wires (yes the wire map failed but it passed everything else). I had to move a wire that was tied to a conduit at a sports bar that was causing issues. Of course there are times where this wouldn't have caused issues. Went to a country club and the wire bundle was laid over a steam pipe. Both cabling issues that were certified and the problems solved by replacing and or removing the improperly ran cable.

Bo

Kentucky phone support-
"Mash the Kentrol key and hit scape."

 

[DTSMAN]

Here is a link to a thread about this some time ago.

thread575-660280

Bo

Kentucky phone support-
"Mash the Kentrol key and hit scape."

 

[wires]

Usually this sort of problem is a result of a small number of problems cascading to create a big one. The trick is to determine which cables are at fault. A good place to start looking is in the hub/switch logs and server logs. If he network does not have managed hubs or switches bringing some in would be a good idea.

The Omniscanner2 can do more testing than the simple pass/fail certification test. The idea is to figure out which cable(s) you are having problems with and check for noise etc. I have been known to bypass a suspect cable with a long patch cable to see if that cleared the problem up.

Excellent link to the prior thread. Both Daron and Servamatic have some excellent points. Like Daron I have never seen a cable that could pass certification with flying colors be the root of network problems. Servamatic's point about when the testing was done is important to remember. Just because the cabling passed certification when it was installed is no guarantee that it still does. A installer of a company I used to work for would let 2 stories of RG6 weigh on the point where the cable passed over the top plate. Two years latter those RG6 cables would no longer pass a satellite signal.

 

[oldtimerbob]

There are other testers out there too, such as the Pentascanner and Wirescope.

The key is always the installation,as the cable installation compamy should always follow certain guidelines.
1. the max pull pressure allowed 21 ft Lbs
2. Go as high as possible and/or use the 12 inch rule ( leave a foot all the way around away from other things in the cable runs from the data room to the stations,if possibe like Air Conditioning units,etc )
3. At least 3 ft away from any power generation equipment,such as electricial boxes in those areas
4. Use 'J' hooks or cable 'cradles' to support the cabling
5. Terminate the cable within 1/2 inch from the end of the cable to the termination point (jack/patch panel)

Failure to do these will effect your performance after a period of time, tho the cable will pass even the most strict test (most of the time) at the time of the orginal install due to the cable being new.

 

[aarenot]

If your scanner compiles data on the cable run being tested, look at the results of each test. Check where the run falls in the pass fail range for each run. Chances are, you will find a run that passes, but has little margin, eventualy, it can fail. You can set the criteria for pass/fail on most I have used. Set your pass fail criteria to fail some slightly passing cables. This is easier than going back in after, and running new cable. It makes life a bit tougher when running cable, but easier when the install is 2 years old.
Nothing wrong with setting your standards higher than industry. Also, since we had to submit print outs of the scans, IT guys got to know our standards were higher than industry, and our competitors. They wanted us to run their cable, and worried less about low bids.



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