topic Cable lenght in Switching

Cable lenght

Sewanna — Thu, 11 Jan 2024 20:01:44 GMT

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?

Re: Cable lenght

aleabrahao — Thu, 11 Jan 2024 20:54:22 GMT

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

Re: Cable lenght

MerakiGnome — Fri, 12 Jan 2024 10:09:44 GMT

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

Re: Cable lenght

Sewanna — Fri, 12 Jan 2024 18:37:12 GMT

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

Re: Cable lenght

Sewanna — Fri, 12 Jan 2024 18:38:58 GMT

External companys are responsibility for that.

Re: Cable lenght

aleabrahao — Fri, 12 Jan 2024 18:39:48 GMT

I suggest you open a support case to confirm.

Re: Cable lenght

MerakiGnome — Fri, 12 Jan 2024 19:06:44 GMT

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

Re: Cable lenght

CMR — Sat, 13 Jan 2024 19:42:02 GMT

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

Re: Cable lenght

Sewanna — Sun, 14 Jan 2024 19:11:59 GMT

43-50 meters, and Meraki 90-100 meters

Re: Cable lenght

aleabrahao — Sun, 14 Jan 2024 19:37:51 GMT

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.