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!
Edit: this is the cable https://a.co/d/i6mYLy1
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Did you ever figure this out? I’m curious. Nobody mentioned the caulk, yes you cleaned it, but if it was silicone then it likely cures with acetic acid, which can corrode the conductors on both sides of the plug.
I think I’ve figured it out, but have not fixed it.
I’m fairly sure it’s a ground loop type issue. It comes and goes. It ran at 1Gbps for a few weeks at one point and I thought it was resolved, but it’s now back to 100Mbps.
I have a few options - I have a pair of Ubiquiti airmax gigabeams that I can put back into service, I can dig a shallow trench and bury some fibre (it only recently occurred to me that fibre is not electricity so doesn’t need to be down 2’) or I can dig a shallow trench and bond the ground between the two buildings.
The gigabeams are obviously the easiest, the fibre is the best (and what I should have done in the first place) and bonding the grounds would only really be out of curiosity to see if it actually works.
And with your advice I have another option - double check the contacts for cleanliness and possible corrosion.
Thanks for the update!
I’m not a professional, just some ideas here:
Yes cat6 is copper, but it’s low voltage, so according to a quick Google, you can put it 6 inches under and be ok, depending on what’s on the ground above it.
Fiber sounds good, but more delicate if anything is driving over it, might want it deeper anyway. For what it’s worth they just installed it at my house and only trenched it 2 or 3 inches, so 🤷♂️
You mention bonding the buildings together, and that might work, but there might be some code violations there, definitely look into it. IIRC if bonding two buildings, you need to, at a minimum, drive a ground rod 8ft down every so many feet. On every 5 or 10 maybe? Don’t quote me, definitely look it up.
But you might not need to do that anyway, did you try grounding just one side, or the other side? Just making sure the shielding on one side or the other is bonded well to the ground in that one building, and not the other. RF can do some weird stuff. And a wire that long is basically a big antenna, and if not grounded, can be inducing all kinds of voltages and noise where it shouldn’t be.
The RF link did work great, but it’s hard to beat a solid chunk of wire. That REALLY should be working for you, sorry to hear it’s not.
Anyway sorry to butt in with my opinions, please do keep us posted! I’m quite curious now haha
sorta curious but why did you opt to bury the cable rather than run a pipe that you could run cable through?
Not op, but sometimes you just do the quick easy thing with the assumption that it should be fine for a good long while. And then it isn’t 🤦♂️
I’d had good luck running similar length copper outside, between buildings, in the past. I had regular blue indoor cat5 just under the surface, tacked to the bottom of fences etc for 7 years and never had a problem with it. Dropping a roll of pre terminated cable built for direct burial in the trench seemed like a no brainer.
With the benefit of hindsight - having that 4’ deep trench open was a once in a lifetime opportunity that I should have better taken advantage of.
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.
Earth leakage
Imagines a burst pipe flooding the room with dirt
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!
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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.
Unplug both ends and use a multimeter to check resistance between the individual wires at one end. Should be OL (out of limits) on screen.
Try earthing one end as slazer2au said. The cable may be bringing in stray voltage thats messing with the device.
84m for pairs sounds right on a 76m cable when you adjust for the twists.
Some devices can push distance better than others. The cisco has eee and a short range option from memory. Make sure you turn all off on the port in question.
Try the link with a pair of laptops.
Cut off the connectors and determinate.
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.
Reterminate both ends and try again.
Do you have a cable tester?
