EEVblog® Electronics Community Forum
Electronics => Repair => Topic started by: Alex_Baker on February 18, 2026, 11:13:36 pm
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Hello people
Not sure if this is the right place for this but here we go. I am working on running a couple of ethernet cables around my apartment, they are no more than 35 feet (~10M) in length. I cut the cables to length and terminated them myself, which I have done a dozen times. BOTH of the cables I made today do not work at all, the connected devices and router act like there is nothing plugged in at all. Running a different cable across the floor for testing shows that there are no problems with the router or device.
I have pretty limited tools, basically just a multimeter, so I shorted the color pairs on one end of the cable and tested resistance. I found that each pair measured about 14 ohms (7 ohms one way). According to my research this is a bit high, the working cable measured about half of that.
So clearly there is a problem with either the cable or the terminals that I bought from amazon. I hope there are some people on the forum that can give their thoughts on this issue, I dont want to buy more cable and connectors without identifying the problem first. The cable, crimp connectors, and crimper are all ones I have not used before, but are all pretty standard as far as I can see.
Thanks!
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My first thought would be a pair got flipped, especially if you only tested with the multimeter. Do you have an ethernet cable tester? You'll want at least a basic one that tells you if it's wired correctly. But you could also use your multimeter to eventually figure this out if you can't see the colors clearly, assuming you can get both ends near each other.
Some other issues off the top of my head:
- not inserting the wires fully into the plug
- not using the right cable (or wire gauge) and/or plug
- sometimes one of the plastic dividers on the plug gets bent over preventing contact once inserted into the jack
To clarify on cable, solid core is only for infrastructure wiring where you punch it down to the patch panel and wall jacks, stranded is for patch cords.
For the plug, there are two types and using the wrong one can sometimes lead to issues. For solid core there are two offset points where it essentially straddles the single copper conductor; for stranded it's typically two points that are in line with each other so they can contact multiple strands near the middle. Putting a plug on solid core is frowned upon, but of course we do it when we have to.
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I tested the cable by shorting pairs on one end, and using the multimeter on the other to test each pair individually. I double checked that each end was the same, unless I dont understand what you mean by a "flipped pair". I am following the T568B configuration.
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Hi.
There's tons of differences, even though the outer dimensions of the cables and connectors may be the same.
As you said you made cables before, i guess you are using the correct mapping of the pairs to the pins on the connector (?)
It doesn't really matter which pairs go to which "pin pair", as long as you keep the mapping correct.
Mapping means the wires do not go into the connector like 1-2, 3-4, 5-6-7-8 (more like 1-2, 3-6, 5-4, 7-8 if i'm remembering right)
There's cables with stranded or with massive cores, and there's different core sizes.
You need to match the connectors to any of these properties for the most reliable results.
There are also different ways the pins cut into the wire, mostly 2 or 3 "teeth" on it, i'm not sure if there is a better one out of these and which that better one would be.
So first thing i would do is to see whether the core sizes and the (holes in the) plug are corresponding.
If the holes are too small, the cores will not fit, and if they are too large, there will be a bad connection even though your multimeter beeps during its continuity test.
Next would be to see if you have stranded or massive cores, and if the connectors are made for the cores you've got.
I hope this helps.
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Well I found part of my issue, I ran both of the cable runs within inches of a wireless access point :palm:
After moving the cables there was some activity, but very sporadic and unpredictable. I may have a mismatch between cable and terminations. My terminations are designed for stranded, but I think the cable I got is too small, something like 32AWG.
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32AWG? I've never heard of ethernet cable that small. Is this actual ethernet cable or some other 4 pair cable? Is it CAT5 or CAT5E?
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Well I found part of my issue, I ran both of the cable runs within inches of a wireless access point :palm:
No, that is not the problem. Obviously you can run Ethernet cable to within 0 inches of an access point.
You really need to get a cable tester, or just buy a couple of premade patchcords.
Yeah you are right, how else would you hook up to an access point.... Interestingly it seemed to have an effect in my case, probably because the cable was very marginal to begin with. I originally chose to terminate my cables myself because I needed to run it through a hole, but I have since found an alternative route.
32AWG? I've never heard of ethernet cable that small. Is this actual ethernet cable or some other 4 pair cable? Is it CAT5 or CAT5E?
The cable calls itself CAT5E patch cable, maybe I just ended up with some really crappy amazon cable while not paying enough attention.
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I think the cable I got is too small, something like 32AWG.
Twaddle. I have 30 and 32awg tinned copper here and it's like hair. There is absolutely no way a crimp terminal could terminate that stuff unless it was something like 30awg x 7 (minimum). Also, close to a WAP is bullcrap. It clearly sounds like you have no idea what you are doing. Know what you don't know. Employ someone who actually knows.
A TDR cable tester is bugger all on the usual crap auction/sales sites. Buy one and get a clue.
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Ooof, harsh, Brad!
If you shorted the orange & orange/white at one end and checked the resistance at the other end, you would get a reading even if the orange from one end went to where the orange/white was supposed to be on the other end. So it's not a valid test. A valid test would be if you could get both ends next to each other and check the continuity on pin 1 only, etc.
In many cases you can see through the RJ-45 plug to determine if the colors are all 100% correct, but some times you can't. So a cheap continuity-based Ethernet cable tester is really a must-have item.
You could also post Amazon links to the products you bought so we can see for ourselves if anything is suspect (supplies and tools).
And photos wouldn't hurt either.
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Ooof, harsh, Brad!
Not really. If you don't know what you don't know then you'll never know what you need to learn. If it was in the beginners section, maybe I was a bit, but it isn't.
If you shorted the orange & orange/white at one end and checked the resistance at the other end, you would get a reading even if the orange from one end went to where the orange/white was supposed to be on the other end. So it's not a valid test. A valid test would be if you could get both ends next to each other and check the continuity on pin 1 only, etc.
Or you could use a cheap arse RJ45 tester that hits all pins in a sequence and you watch the results on LED's. Cheap, cheerful and lets you know quickly if you've fucked it up. Even Chinese TDR based units that give you an actual wiring map *and* an estimated cable length are worth maybe 10 pre-made patch cables.
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Resistance suggests AWG30 wire, CCA on top of that. Such substandard thin wires won't crimp properly in most of Cat5e connectors and zero chance with Cat6 connectors.
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Brad, you didn't get the hint, so I'll be more clear: go find another topic to play around in. It's obvious you're in a bad mood.
And you've just repeated what I already suggested, which was a tester, but obviously the OP doesn't have one, so an alternate method was presented using what they have on hand.
Resistance suggests AWG30 wire, CCA on top of that. Such substandard thin wires won't crimp properly in most of Cat5e connectors and zero chance with Cat6 connectors.
Definitely plausible and with copper prices it's even more likely the cables are suspect. But also the OP could have just guessed at the wire gauge.
Also, depending on how the other end was "shorted", this could just be some contact resistances adding up, especially if oxidation is present (at the short and/or at the DMM test leads). So maybe a red herring.
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Yeah Ethernet cable quality matters a lot as soon as you go longer distances.
It is more than just having continuity on the wires. The dimensions of the wire and insulation have to be exactly right to get the correct characteristic impedance of 100 Ohm. The pairs need to be each twisted a different amount to reduce crosstalk problems. The material used for insulation determines how fast the signal gets lost. The good cables have shielding (foil or braid or both) even better cables have shielding on each pair individually.
It is not worth buying the cheapest Ethernet cable they have on offer. For the distances typical in residential settings it doesn't cost that much more to buy the high quality brand name cable and know it will be reliable for decades to come.
Also as mentioned above if you have cable that is too far away from the spec then it might not work well with punch downs and crimp connectors. They are designed for the wire conductors being a specific size, If they are not then it might not make a solid reliable connection, even if it does have contact right now, it might loose it once you bend or tug on the connector.
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Just to help (hopefully) help you know what is important:
1) "normal" Network cable (CAT5 or later) is all somewhere around 24AWG. Although you can find networking patch cables which are smaller, standard cable usable with standard ends will all be about that size.
2) Matching CAT rating and stranded/solid and shielded/unshielded are all important when selecting ends for a cable. Using stranded cable with crimp-on-ends that are only for solid doesn't work. Trying to use CAT6 in a CAT5 end often doesn't work due to the wire dimensions/sizes being different. And so on.
3) The ethernet standard assume you have stranded patch cables at both ends and solid in the middle. Although that's the standard, it's perfectly acceptable to just crimp an end on Solid cable. But it needs to be a connector designed for that. Not having the stranded patches at each end aren't going to affect performance - using stranded for a long run including the middle might.
4) It is critical that you put each pair of wires in the right spot on the cable. I'm not talking "same spot" at both ends, but that you have a pair on 1,2. And another pair on 7,8, and another pair on 4,5 and finally a pair on 3,6 (note these aren't next to each other). If you instead put a pair on 1,2, another on 3,4, another on 5,6 and the last on 7,8, the cable won't work correctly. There are standards for which colors of wires go on each pin, follow them and this will work out correctly.
5) a properly terminated cable is pretty much impervious to any external interference you're likely to encounter in a house - power strip, extension cords, wifi router, etc.
6) Having crimped (or troubleshot someone else's crimping) way too many times in my life - the crimper and ends being of decent quality and compatible with each other (and the wire) is important. Buying expensive tools and ends don't guarantee this. I.E. there is very little correlation between acceptablity of a tool and it's price.
7) I don't know about your budget here - or what you have, or if this is available in your country, but I will make a recommendation of a specific example of a tool kit I like. Klein makes a VDV226-107 crimper which works really well with klein branded passthrough ends. In addition, there's a klein VDV526-200 tester which will check for all of the common miswires. You can often find a kit with the tester, crimper, and ends for around $100 total. This should be a "lifetime" purchase unless you're using this professionally.
8 ) Don't feel obligated to buy the specific kit in #7. It's just one I've finally found that is a good combination of "cheap enough to be affordable" and "expensive enough to work". It's more an example than a "you must buy this crimper".
9) The passthrough ends in #7 can be controversial as some people have had bad luck with them, but I find that I fight them a lot less than I do a standard end. With these, when making up the cable you push each wire all the way through the connector and then can tug on them, make sure they're in the right spot, and everything before you crimp it. The crimp cuts the ends off as part of the procedure.
10) If I was to guess what is wrong in your setup: Either you have the wrong cable, or wrong ends for that cable - with a small chance that you have a split pair (meaning pairs aren't in the right spot even though you have end-to-end connectivity). The reason I say there's a small chance for the split pair is that at the lengths you're working, the pairing being acceptable is less important. On the other hand, you saying that that the position of the cable matters is a good argument for the split pair issue.
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If you follow the rules it's not that hard.
1. No CCA for runs over 10 meters.
2. No plugs on solid core.
3. No stranded wires into LSA punch-down boxes.
4. Follow the same TIA-568 on both ends.
5. Avoid shielded cable unless you really need to and know where to tie the shield to ground.
6. Minimize the number of "turns" your have untwist a pair.
7. No sharp bends.
8. Test before use, it's so easy to accidentally have one of the green and blue mixed up in a plug, then the cable doesn't work
If this all goes okay and the cable still does not work, there is probably a defect in the cable that doesn't show up in DC but prevents the HF to work properly.
For example a tiny in-line copper break due to bending, pulling or standing on it. DC has no issues with it, but the HF will reflect and interfere.
Some switched or NIC have a cable test that can detect the distance of this defect and what pair it's on.
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2. No plugs on solid core.
This really isn't a requirement.
I can guarantee that almost every PoE-powered camera, outdoor radio, commercial wireless access point, and so on is connected to the network using a standard RJ45 crimped onto the end of a solid cable.
Solid is the better, more reliable cable for the signal in an Ethernet system. But what it isn't good for is flexing and being handled regularly by humans. As a result, the Ethernet spec allows up to 10m of patch cable total across both ends of an Ethernet link, so you can run solid to a jack on the wall and then use a stranded patch cable from there to whatever device you're using. And potentially from the switch to the patch panel on the other end.
But.... the permitted use of the stranded cable at both ends is there for convenience and cable robustness not for anything affecting signal integrity (at least until you mangle the connector which is easier on solid). It also is the correct way to do this in a commercial installation where you're going from a patch panel in a wiring closet to a fixed jack on the wall.
If you're running a cable over about 10 meters, it should be solid. If you are plugging it into something that won't move or be regularly plugged in and unplugged, crimping an end onto a solid cable is perfectly acceptable. Which is why it's the way that cameras and the like are done. The solid cable gets pulled to the location the camera needs to be, an end is crimped on it, and it is plugged directly into the camera. Once installed, it isn't touched again until the camera is replaced for any reason.
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I think the cable I got is too small, something like 32AWG.
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A TDR cable tester is bugger all on the usual crap auction/sales sites. Buy one and get a clue.
Would you have a suggestion for a cheap ethernet TDR on aliexpress or ebay?
Most of what I see are not in the usual impulse buy pricing one would consider for a single job.
I'll also echo the question about the exact cable and connectors bought on Amazon.
To figure out what it is and if it could be the issue.
I have seen the flat, unshielded cables being sold in 25meter lengths or more with "cat6a" prints on them cause problems with 1GbE.
Do the latest Ethernet standards finally give any definitions or requirements for CCA (Copper Coated Aluminium) and CCS (Copper Coated Steel) "Ethernet" cable?
Or is the standard still copper only?
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I have a cheap "Ethernet installation kit" I got off Aliexpress for around $30 (stripper, cutter, crimper, continuity checker, etc.) and a big bag of "crystal heads" for $5, and have terminated around a dozen cables with it that are perfectly usable at 1Gbps, with the longest being around 150'. Cable was cat5e, no real brand, also from the same place.
The OP needs to post some pictures of what he has.
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Don't go cheap on the cable. Buy a known brand, not cheap chinese crap on Amazon. Solid core is best. If in doubt, buy a used cable on ebay and cut to length.
Or go simple and buy a 10m cable.
And you really want a crimping tool, even a cheap one is good enough. You can't do the plugs without a tool, that rarely works at all.
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Would you have a suggestion for a cheap ethernet TDR on aliexpress or ebay?
Most of what I see are not in the usual impulse buy pricing one would consider for a single job.
The Uni-T UT685B seems to get good reviews at USD100-150. AliEx obviously has better deals than Amazon or eBay, but not as convenient. I have not tried one myself as I have a Fluke CableIQ.
I do have a few of the cheap sequenced continuity testers, with my most recent one supporting both RJ45 and HDMI connections. So it will cycle through either 9 or 20 conductors (including shield), and I imagine this means it could be easily repurposed for testing your own cable harnesses. Powered from single AAA or a microUSB supply. If anyone is interested: https://www.aliexpress.com/item/1005009191148668.html (https://www.aliexpress.com/item/1005009191148668.html)
I agree with others that cable quality is going critical to getting good crimped connections, and for longer runs you will want a higher gauge especially if doing PoE.
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Honestly, I don't think you need a tester. I installed multiple kilometers of networking cables, lots of terminals and crimped quite a few plugs. I think I had a non-working crimp only twice or so. Easily diagnosed without tester.
Just stick to the colors, push them all the way in, crimp, done. For only a couple of meters and low-ish speed, you don't even need to take care of shielding, making this even easier. If the cable does not work, cut off the plug, repeat. Modern switches (newer than, say, 20 years old) even do auto-crossover, so not even required to have different cables made.
And again, for proper installation you need proper cable, and a crimping tool.
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If you follow the rules it's not that hard.
1. No CCA for runs over 10 meters.
2. No plugs on solid core.
3. No stranded wires into LSA punch-down boxes.
4. Follow the same TIA-568 on both ends.
5. Avoid shielded cable unless you really need to and know where to tie the shield to ground.
6. Minimize the number of "turns" your have untwist a pair.
7. No sharp bends.
8. Test before use, it's so easy to accidentally have one of the green and blue mixed up in a plug, then the cable doesn't work
If this all goes okay and the cable still does not work, there is probably a defect in the cable that doesn't show up in DC but prevents the HF to work properly.
For example a tiny in-line copper break due to bending, pulling or standing on it. DC has no issues with it, but the HF will reflect and interfere.
Some switched or NIC have a cable test that can detect the distance of this defect and what pair it's on.
This is great advise
One nit pick, thing I would add is in the US standards twisted pair category cable should be 100% copper, and no smaller than 26 AWG. Typically you want 24 AWG copper. Any Copper Clad Aluminum (CCA) would be a violation of the NEC (National Electrical Code) section 800.179. Probably other national standards have the save verbiage. EN 50288-1:2003, 4.1. states "conductor shall be annealed solid copper", just FYI there is a lot of CCA cat5/6 sold online and few places where it would be legal to install.
Cheers
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If you shorted the orange & orange/white at one end and checked the resistance at the other end, you would get a reading even if the orange from one end went to where the orange/white was supposed to be on the other end. So it's not a valid test. A valid test would be if you could get both ends next to each other and check the continuity on pin 1 only, etc.
I should have been more specific describing my testing. To test each pair I took a PCB mount RJ45 socket and shorted pin together, specifically; 1 & 2, 3 & 6, 4 & 5, and 7 & 8. Since I used a PCB socket with the crimped end plugged into it I was sure that the pairs were going to the pins that I expected, and that each pair had continuity all the way through the crimp. I did eventually pull the cable from where it was installed and measure continuity with the ends next to each other, testing pin to pin, I didn't learn anything I didn't already know.
Unfortunately I do actually have a tester, it just happens to be at my parents house currently where it doesn't do me much good here. I rarely crimp ethernet cables so buying a tool kit is not really worth it, the main reason that I do it instead of buying pre-built cables is because I wired all the bedrooms in my parents house with ethernet, so I had all the tools and a large spool of decent cable at their house.
Don't go cheap on the cable. Buy a known brand, not cheap chinese crap on Amazon.
As many others have said I think this is where I failed. This is the cable I bought: https://www.amazon.com/dp/B01G0LUS90?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1 (https://www.amazon.com/dp/B01G0LUS90?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1)
Not sure why I chose this one, I think I specifically wanted round white cable, when most of the ones that popped up were flat. Either way it apparently was "cheap Chinese crap on Amazon", despite pretty good amazon reviews. When you scroll all the way down to the description it does actually say that it is copper clad wire but not what gauge it is, which is seriously somewhere around 30 - 32 awg. It should be noted that I cut the 100ft cable I bought into two 30(ish) foot sections and re-terminated it. This does make me curious to know if the cable worked right out of the box.
Hopefully this will answer some questions, but so far it looks like the cable quality is the most suspect. I really appreciate everybody's input, thanks!
Also I hope Brad's day got better :-DD. I had a brain fart with the access point thing, it threw me off that a cable I was messing with started to work when I moved it, however in hindsight I think the cable actually was not working, but the indicator lights on the computer came on ,which they never did before moving it.
TLDR: crappy cable, poor judgement on my part. :-+
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Crimping your own Ethernet cables is a false economy. If you buy preterminated patch cords from Cable Leader or Bestlink Netware, you won't have problems.
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There are cases where you have put a new end on, such as if the hole isn't large enough for the plug to fit through. Also, if you have a very nice, expensive patch cord but break the retention clip off, why throw away the cable when you can just put a new plug on it?
With regard to shorting the pins as a test, my point is that if you shorted pins 1 and 2 at one end, but at the other end they were inadvertently reversed (2 and 1 instead), then you'd have continuity, but the cable wouldn't work because it's wired incorrectly. So it's not a valid test. Testing each pin individually will be accurate.
The smaller gauge wire and the fact it is copper-clad are problems, but as with most of those cheap items it will work for a lot of people. So that probably explains the good reviews (along with probably a lot of fakes). The smaller wire might be an issue with higher power PoE devices, but I don't think it would prevent link. Really just a thought experiment at this point, though.
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It should be noted that I cut the 100ft cable I bought into two 30(ish) foot sections and re-terminated it. This does make me curious to know if the cable worked right out of the box.
Probably yes, and you likely tried to use plugs for solid-core whereas pre-terminated cables are usually stranded (and as you found out, far too thin for regular plugs.)
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Crimping your own Ethernet cables is a false economy. If you buy preterminated patch cords from Cable Leader or Bestlink Netware, you won't have problems.
You don’t crimp your own patch cables to save money, you do it to get custom lengths that aren’t available, and for situations where you can fit the cable — but not the connector — through a small hole, requiring you to terminate the cable after installation.
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It should be noted that I cut the 100ft cable I bought into two 30(ish) foot sections and re-terminated it. This does make me curious to know if the cable worked right out of the box.
Probably yes, and you likely tried to use plugs for solid-core whereas pre-terminated cables are usually stranded (and as you found out, far too thin for regular plugs.)
Patch cords are indeed normally stranded, and since patch cords are the far more common use for RJ45 plugs, the default type of plug is for stranded, not solid. So I would say the “regular” RJ45 is the kind for stranded, not solid. Looking at digikey’s selection of RJ45 plugs, the overwhelming majority are either for stranded wire only, or for stranded and solid wire. Only a tiny percentage (under 4%) are for solid wire only. So the chances that OP has a solid-only plug is relatively small.
The standards require the wire to be 26–22 AWG, but some connectors nonetheless support 28AWG. What does seem to be slightly rarer is support for 22AWG.
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1. No CCA for runs over 10 meters.
Don't go cheap on the cable. Buy a known brand, not cheap chinese crap on Amazon.
As many others have said I think this is where I failed. This is the cable I bought: https://www.amazon.com/dp/B01G0LUS90?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1 (https://www.amazon.com/dp/B01G0LUS90?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1)
Not sure why I chose this one, I think I specifically wanted round white cable, when most of the ones that popped up were flat. Either way it apparently was "cheap Chinese crap on Amazon", despite pretty good amazon reviews. When you scroll all the way down to the description it does actually say that it is copper clad wire but not what gauge it is…
FYI, the Cat 5 and higher standards require the cable to be 100% copper, so any CCA wire is by definition not compliant. And if they didn’t follow the materials requirements of the standard, what other aspects of the standard did they also ignore?
At least that Amazon listing is “honest” insofar as they admit to using CCA, though it’s then a lie to claim to be Cat 6 cable. So I doubt it actually meets Cat 6 performance requirements, and your experience with it being susceptible to interference supports this.
Note also that the super-thin flat Ethernet cables also aren’t compliant. They may claim to be Cat 6 or whatever, but they don’t adhere to the standard. They might be able to perform well enough (possibly even enough to pass tests), but nonetheless they’re not complaint to the standards. For example, this one (https://www.l-com.com/category-6a-10gig-ultra-flat-ethernet-cable-assembly-rj45-male-plug-u-ftp-shielded-pairs-32awg-stranded-cm-pvc-jacket-black-35ft-trd632asflat-blk-35f) from a reasonably reputable manufacturer is claimed to be Cat 6a, and being a reputable brand it probably meets the performance targets, but it’s also specified as 32AWG, far thinner than the standard allows.
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I have terminated dozens of Ethernet cables. I have the crystal connectors and I have the habit of putting connectors on scraps of cable.
Before crimping I very carefully check the colors are correct. I double check and then I crimp. Then I just test the cable between a computer and a router. Half of the times it doesn't work. Then I check the colors and I detect a mistake which I did not detect before crimping. So I cut off the RJ45, install a new one correctly and now it works. I don't know how this happens to me so often but it does.
I have several crates of cables which I do not really need but I still have this graphic on my computer desktop ready for any new crimping.
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Something like this is handy : https://www.noyafa.com/products/nf-308s-wire-fault-locator (https://www.noyafa.com/products/nf-308s-wire-fault-locator)
It checks wire sequencing and gives you a fairly accurate estimate of the length of each pair. We had a rat attack a cable in the roof. It had a run length of > 40M. By checking pair distances from each end I could estimate the break within about 3 roof tiles. Great for a quick check of patch leads after crimping too.
I bought the standard model about 15 years ago. About 5 years ago I upgraded to the "fancy" one with 8 dongles. Just go around the place and plug them all into the wall, then run the tester down the patch bay to identify the sockets. A few friends have moved into houses with un-labeled cables or had connectivity issues. Something like this makes it easy, and is slightly more useful than the "running led" testers.
The warbler has come in handy too, mainly for tracing sprinkler solenoid cables, but also the odd figure-8/coax/whatever.
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I've been crimping since the 80s and realistically you can get plenty far with just the $5 cable testers to tell you if you've goofed or not. With UTP Ethernet, once you establish link, the quality of the cable can become evident if it's supposed to be gigabit but only establishes 100M. I've also seen plenty of kinked UTP and cables run over dozens of light ballasts and it frequently surprises with how well it works.
I think a lot of this changed with the introduction of 10GBASE-T because it had steeper requirements. You could do it with proper quality CAT5e over very short distances, but longer required higher and higher cable standards. Shielded cable was also popular. Installers were testing and certifying the cable to make sure it met the requirements for 10GBASE-T. You had customers sometimes going years before discovering that they couldn't actually run 10GBASE-T. This is because they may not have had 10GBASE-T to the desktop initially. So the high-frequency certs were important. Also, the next fallback rate would have been 1GBASE-T which would be pretty disappointing.
Things have changed again with 2.5/5GBASE-T because it can run over CAT5e and will auto-negotiate the link based on what the cabling/switch/device can actually do. If you have a very large building with thousands of drops, you're not going to want to pull new cable unless you have to. So you slap new switches and Ethernet cards in (although many computers in the last 5+ years have 2.5GBASE-T). Whatever you get for the speed is what you get. Personally in the building I work in, we've seen great results and so far are getting solid 10GBASE-T over CAT5e. Users with 2.5GBASE-T NICs are also happy with the speed boost.
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Getting one of those fancy testers is overkill if you are just a hobbyist doing just a few cables a year. I agree that a $5 multimeter and a little time are enough to diagnose the most basic problems.
When I terminate a cable I just connect it to a computer and router and if it works I consider it good. If it doesn't work I double check the wires are connected to the correct pins and this is usually the problem.
Very rarely I find it is the cable itself which is at fault. To check the cable, for ease connecting to the RJ45 connectors, I have a couple female connectors with the wires bare where I can connect alligator clips. This way it is very easy to detect continuity and shorts.
Some months ago I detected a bad cable where one faulty wire had no continuity. I have plenty of cables and I did not need to repair this one but, just for fun, I cut it in half and put an RJ45 on the half that was good. Then I cut the other in half and, again, terminated the good half. I did this until the last bad piece was so short it was not worth continuing.
For more serious or frequent work it would be very easy, and basically free, to construct a board with two female RJ45 connectors and some LEDs confirming continuity and correct connections.
And now anecdote time. About 25 years ago I was in a cheap hotel in China and my Ethernet Internet connection was not working. I talked to the young woman at the front desk and she called some maintenance guy and they both came to my room and the guy plugged in some test device into the wall and there were some blinkenlights showing the cable was connected at the other end. The guy did not speak any English and the young woman was translating as best she could, which was not much. The man, who I think did not know much about anything, said the wires had been eaten by rats in the walls and ceiling and the receptionist offered to change me to another room but I said before we do that let us test the Internet connection in the other room ... and it wasn't working either. The guy insisted there were many rats eating cables. I think he had a basic Ethernet tester but had no idea how to use it. I suggested to the receptionist they reset the router but the guy was adamant. Rats were everywhere. I think he really had no idea what the router was. I told the girl that it did not make a hotel look good to tell guests the place was full of rats.
After some further talk the guy left and after much more talk I convinced the young girl to find out where the router was located because she had no idea and had to ask around. Finally she accompanied me to a small service room in the attic and there we found a woman eating her noodles and, in a corner, the router. I reset it and magically all the rooms had Internet connection again. The cheap router had a habit of hanging because during my stay I had to repeat the operation several more times. The receptionist was grateful that she now could solve the problem so easily even if it meant going to the top of the building.
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With regard to shorting the pins as a test, my point is that if you shorted pins 1 and 2 at one end, but at the other end they were inadvertently reversed (2 and 1 instead), then you'd have continuity, but the cable wouldn't work because it's wired incorrectly. So it's not a valid test. Testing each pin individually will be accurate.
Ahh I see, that makes sense, thanks for the clarification. Like most my cable ends are clear so I can see the wire colors to verify them, but you are correct, my test would not be valid in this case.
Note also that the super-thin flat Ethernet cables also aren’t compliant. They may claim to be Cat 6 or whatever, but they don’t adhere to the standard.
Funnily enough this is exactly what I bought in patch cable form to replace the crap that started this thread. In my case I don't expect issues since the cable is just running to a Raspberry Pi that is controlling a 3D printer. I also did not re-terminate any ends and in this instance the flatness makes it look nicer along baseboards and above door frames.
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I have terminated dozens of Ethernet cables. I have the crystal connectors and I have the habit of putting connectors on scraps of cable.
Before crimping I very carefully check the colors are correct. I double check and then I crimp. Then I just test the cable between a computer and a router. Half of the times it doesn't work. Then I check the colors and I detect a mistake which I did not detect before crimping. So I cut off the RJ45, install a new one correctly and now it works. I don't know how this happens to me so often but it does.
I was gonna say… if that really is a frequent occurrence, then something is wrong with how you’re “carefully double check[ing]” the colors before crimping, and/or with how you’re moving the connector into the tool to crimp it. (Are wires pulling out and then being pushed back in, potentially in the wrong order, when you put it into the tool?)
I’ve crimped perhaps 20 cables over the years (and installed a bit more with punchdown jacks) and I’ve never had a failure, so this isn’t a “normal” problem. ;)
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I think a lot of this changed with the introduction of 10GBASE-T because it had steeper requirements. You could do it with proper quality CAT5e over very short distances, but longer required higher and higher cable standards. Shielded cable was also popular. Installers were testing and certifying the cable to make sure it met the requirements for 10GBASE-T. You had customers sometimes going years before discovering that they couldn't actually run 10GBASE-T. This is because they may not have had 10GBASE-T to the desktop initially. So the high-frequency certs were important. Also, the next fallback rate would have been 1GBASE-T which would be pretty disappointing.
I recently upgraded my home internet from 600/60Mbps cable to 10Gbps fiber-optic (with WiFi 6 in the new modem/router/gateway), and this means I will eventually also need to upgrade the second access point on the other end of my apartment. (Several heavy masonry walls means WiFi can barely make it from the living room to bedroom.) I have it connected with an Ethernet “backhaul” to the bedroom, which I ran years ago using Cat 6a (maaaybe cat 7? I don’t remember). It’s worked perfectly for gigabit, but until I actually get a 10Gbps access point and Ethernet switch in the bedroom, I won’t actually be able to know whether it actually supports 10Gbps. It’s not a very long run, so I expect it’ll be fine, but still, it’d be great to know.
P.S. I once knew a network admin who had a pet cat named “five”. 🤣
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Something like this is handy : https://www.noyafa.com/products/nf-308s-wire-fault-locator (https://www.noyafa.com/products/nf-308s-wire-fault-locator)
It checks wire sequencing and gives you a fairly accurate estimate of the length of each pair. We had a rat attack a cable in the roof. It had a run length of > 40M. By checking pair distances from each end I could estimate the break within about 3 roof tiles. Great for a quick check of patch leads after crimping too.
I bought the standard model about 15 years ago. About 5 years ago I upgraded to the "fancy" one with 8 dongles. Just go around the place and plug them all into the wall, then run the tester down the patch bay to identify the sockets. A few friends have moved into houses with un-labeled cables or had connectivity issues. Something like this makes it easy, and is slightly more useful than the "running led" testers.
The warbler has come in handy too, mainly for tracing sprinkler solenoid cables, but also the odd figure-8/coax/whatever.
Years ago, I bought a WiFi router (d-link I think, but it may have been netgear) that actually had a cable break test built right in: right in the web interface, it displayed the distance to the end of a cable, or the break inside one. This means it had some form of rudimentary TDR (time-domain reflectometer) built in, presumably a feature of the Ethernet PHY. I remember it being accurate to within a foot (~30cm) or so. Unfortunately, that router had other issues, so I returned it and got a Linksys (the venerable WRT54G, which I could put custom firmware onto).
If anyone here knows: Is it common for Ethernet PHY chips to have this TDR function, and most devices just don’t use it? Or was it an oddball?
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If anyone here knows: Is it common for Ethernet PHY chips to have this TDR function, and most devices just don’t use it? Or was it an oddball?
It's very normal (with varying degrees of quality) in managed switch ICs (serious ones, anyway, not one which offer 16 VLANs and a port enable bit), but to my knowledge unusual in end devices - why duplicate the functionality on the other end of the link?
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ADI has some industrial Ethernet PHY that have cable diagnostics.
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I think a lot of this changed with the introduction of 10GBASE-T because it had steeper requirements. You could do it with proper quality CAT5e over very short distances, but longer required higher and higher cable standards.
10GBASE-T via proper CAT 5e can work for a length of around 30 m (if lucky 50 m). Beyond that I'd go for glass fiber (OM4). With CAT 7/8 it's possible to run 25GBASE-T or 40GBASE-T for up to 30 m, but getting the installation of CAT 7/8 right isn't easy.
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Yeah for short enough lengths of a few meters you can get Ethernet working even over speaker wire.
But at 10Gbit Ethernet it does get pretty sensitive. With crappy CAT5e you might start getting issues at 10 meters, or heck even with proper CAT6 and using crappy enough RJ45 wall sockets it might already start having issues.
For anything above 2.5Gbit it is a good idea to simply go fiber. It can do even 40Gbit speeds over larger distances than you would ever need. At the same time even at only 10Gbit the power usage of the transceivers starts getting ridiculous and it might take 5W of power per each 10Gbit link just to keep it connected over copper pair. Might not sound much but once you have 10 links going that's 50W of power being constantly burned to heat just to keep the Ethernet links up. Using a SFP+ fiber transceiver to do a 10Gbit fiber link has considerably lower power consumption and will go past 100m with ease (or even kilometers on single mode fiber), heck fiber cables are even cheaper per meter than good quality CAT6 since no expensive copper is needed.
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If anyone here knows: Is it common for Ethernet PHY chips to have this TDR function, and most devices just don’t use it? Or was it an oddball?
It's very normal (with varying degrees of quality) in managed switch ICs (serious ones, anyway, not one which offer 16 VLANs and a port enable bit), but to my knowledge unusual in end devices - why duplicate the functionality on the other end of the link?
Realtek integrated LAN on many motherboards has this function, can be accessed from BIOS even before booting an OS.
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At work we have multiple 100GbE fiber links and are part of Internet2 (400G is coming). And 40 and 10 all over as well to get that connectivity spread around. But being able to get 2.5/5/10 over Cat5e for users has been a great upgrade for minimal effort.
At home I started adding 10GbE well over a decade ago but just using peer to peer links. Cost, power/heat and noise are typical home lab concerns and I was also able to leverage SMB multichannel with 1G which worked well enough for the rest at the time.
But when Mikrotik released their affordable, passively-cooled CRS30x 10GbE switches in 2019, I jumped fully to 10GbE and I now have six of their switches spread around the house in a hybrid ring configuration.
Absolutely, 2.5/5/10 over copper needs power and generates a lot of heat, so I only use it where necessary and almost everything is fiber or DAC.
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Yep i also got my first 10Gbit switch in the form of a 8 port passively cooled Mikrotik (most of my LAN is Mikrotik anyway) to start dipping my toes into speeds past the classical 1Gbit since i transfer a lot of files to my NAS and such.
The switch itself is impressively low power, but the RJ45 10Gbit SFP+ modules are so power hungry that it gets too hot to touch. I am using DAC cables where possible, but when it comes to Ethernet ports on actual devices like PCs, NAS servers, WiFi APs..etc they are always RJ45, so you are forced to use twisted pair to connect to them. They never seam to have SFP ports, so i bought some old PCIe network cards with SFP ports to solve that, tho a lot of these cards also run pretty toasty because they are mostly made for servers/workstations with a lot of airflow. Makes sense to use 10Gbit over twisted pair to reuse existing cable installations trough the building, but for connecting just 1 devices on the same desk it is a dumb solution, just let us use DAC cable.
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If anyone here knows: Is it common for Ethernet PHY chips to have this TDR function, and most devices just don’t use it? Or was it an oddball?
It's very normal (with varying degrees of quality) in managed switch ICs (serious ones, anyway, not one which offer 16 VLANs and a port enable bit), but to my knowledge unusual in end devices - why duplicate the functionality on the other end of the link?
Realtek integrated LAN on many motherboards has this function, can be accessed from BIOS even before booting an OS.
Having looked at many PHY datasheets for my day job, I'm not sure I've seen a recently designed PHY that doesn't have that feature. I suspect you may get it for free with the cable analysis you have to do with the faster ethernet speeds to make them work, but I haven't dug deep enough into the spec/negotiation to know for sure. (If you have to do a TDR to map reflections to be able to cancel them, then you get the TDR 'diagnosis' function for free silicon-wise).
Now, whether or not it's available to end users vs the hardware being capable of it, that's probably more hit or miss.
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Yeah cable fault testing while usually supported by the PHY is not always exposed as a feature to the user.
Depending on the network card you have the cable test results might be in Device Manager for the card, it might require actually installing some utility program from the manufacturer of the card. Sometimes i also seen the cable test exposed in the BIOS menus.
Similarly switches and routers sometimes provide the cable test results while a lot do not.
You can likely do a actual TDR measurement fairly easily by connecting the twisted pair of interest trough a ethernet transformer as a balun and then send a fast edge square wave into it from a signal generator then use a scope to look at the edge. Where the scope trace is not in the middle of the screen that's where the cable is bad.
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The Electronic Goldmine has these for $9.95: https://theelectronicgoldmine.com/products/g20107