Cable lenght

[AnnaSew]

I doing a cables-lenght test in meraki. Cabels from switch to hosts are 43- 50 long, but in Meraki i see 90-100 meters. Anybody know why? How is this length calculated than it is 2 x longer?

[alemabrahao]

The cable length is determined using TDR (Time Domain Reflectometry):

https://en.wikipedia.org/wiki/Time-domain_reflectometer

It measures the time for a signal to be reflected due to tiny imperfections in the cable termination.  The signal travells at a constant speed, so the length can be calculated.

Accuracy of Cable Test with MS - The Meraki Community

[AnnaSew]

Reflectometer "tells" me 43 meters, but Meraki 100 meters.Could be a bug in Meraki?

[alemabrahao]

I suggest you open a support case to confirm.

[DarrenOC]

Hi @AnnaSew , I would personally get an external company in to check those cable runs.  Sounds like they’ve been incorrectly terminated.

[AnnaSew]

External companys are responsibility for that.

[DarrenOC]

Hi @AnnaSew and what are their testers showing?  Have they stuck a Fluke at both ends of the cable? 

[AnnaSew]

43-50 meters, and Meraki 90-100 meters

[alemabrahao]

To be quite honest, I trust Fluke 1000 times more than the Meraki test. I see the Meraki test more as a quick fix, so I wouldn't get too attached to it.

If in doubt, I would do as I said, open a support case.

[cmr]

What switch model and what firmware are you running?  There was a recent bug with MS130s reporting double the length...