I needed to connect two buildings and was having machines in to dig a 4’ (1.2m) deep trench between them for a water line so I went to Amazon and bought a 250’ (76m) pre-terminated copper Cat6 cable. As I was going to be burying it I wanted to be sure it worked, so I used it as a “fly lead” for my laptop for a week or two first and it worked fine. I know it initially connected at 1Gbps, but (stupidly) I can’t be 100% certain it stayed at full speed the whole time.
Now that it’s buried I’m only getting 100Mbit/s. It does sometimes connect at 1Gbit/s, but it later falls back to 100Mbit/s. I have an old Cisco SG300-10P on one end and a Ubiquiti Edge Router X on the other. I disabled 802.3 Energy Efficient Ethernet (EEE) on the Cisco and, as expected, it made no difference. The Cisco has built in cable test capability and it says I have an 84m open cable on all pairs - even when connected to the ER/X and working. Is there some sort of loopback/test termination I can make for the other end to get a better (more meaningful) result? I’ve tried searching, but failed.
The plug at one end did get pushed through some silicone caulk as it was being shoved through a hole in a wall. I cleaned it off with alcohol and it looks clean, but I’m considering cutting the plug off and replacing it with a socket as my next debugging step as it would be more convenient anyway.
I live about an hour from the nearest large town so there’s no way I’m getting someone here with a proper tester at a reasonable price. If I can’t figure it out myself I’ll revert to the pair of airMax GigaBeam radios that have given me a solid 800Mbit/s for the last 3 years with only visual alignment!
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Reterminate both ends and try again.
Do you have a cable tester?
This is going to sound dumb but I have worked with long cables up telco towers.
Have you properly earthed one of the switches? Not like, the ears are metal and they are touching the metal rack, but actually connected the earth lug on the device to a proper ground? Only do one side because you don’t want earth leakage between buildings.
That does not sound dumb at all. In fact it reminds me that that was the solution to a similar issue I had in the early '90s trying to make an IBM7171 (RS233 terminal attachment unit) work in a different building. I’ll give it a go!
Earth leakage
Imagines a burst pipe flooding the room with dirt
If the Cisco switch says there’s a physical problem, that’s probably it. Since there’s no conduit, you’re not going to be pulling a new one.
The Cisco switch says all pairs are open - which is clearly wrong as it’s working at 100Mbit/s. That’s why I asked about a ‘proper’ termination to get a more meaningful result.
You can reterminate it, sure, but if it’s failing a test at 84m then I doubt it would help. It wouldn’t hurt, though.
Not sure what that means when it’s only a 76m cable, though. Still sounds like a bad reflection.
Is it in a conduit, or buried? Not sure if begin under water would slow it down. Could it have been kinked / damaged? If you can, pull it and test. - for a job like that, run double for future proofing.
It’s cable spec’d for direct burial and it is direct buried. Damage during the trench backfill is the most obvious answer - I’m just making sure I’ve covered all options before abandoning it.
