Have a very odd (and irritating) situation: at my work, there are several CAT5e cables in place that will *only* work when crimped in a certain way (neither T568-A or B ). The *ONLY* way these cables will allow a connection is if they're crimped in the following order:
pin 1 - blue
pin 2 - blue/white
pin 3 - green
pin 4 - orange
pin 5 - orange/white
pin 6 - green
pin 7 - brown
pin 8 - brown/white
And no other way. I have tried using both T568-A and B wiring standards, and I have crimped many many of my own cables sucessfully before using both standards, so I'm positive I'm doing it correctly. And yes, I understand that the individual wires are just copper, and as long as the pairs match up correctly, the ethernet cables should work, which is why I'm even more confused about this.
I've tested the cables in many known working PCs and several working switches. The cables themselves look like regular CAT5e cables, no unusual devilish markings, no kinks, and like I said, they seem to work perfectly ONLY when crimped with the wiring layout I've listed above. I'm at a complete loss here.
Any idea what's going on here, or did I miss something?
Nick
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Have you checked those same cables at a different location?
Are you cutting the ends off and redoing them with the wiring that you posted or are you using an entirely new section of cable? And also, you have cables wired to standards in place working?
Even with all of that I would have to assume the cables are defective. I'd suggest trying them at a different location if you're just thinking they don't work at you work site alone.
Dannah
nickm81us,
"and as long as the pairs match up correctly, the ethernet cables should work"
...while that may sometimes be the case, this really isn't accurate. The twists in the copper pairs are very precise...the reason for this is interference. You see, the interference can actually cancel themselves out (between a pair) if twisted at the right frequency. If you randomly connect the wires (while keeping the pair order the same on both sides...) it *might* work, but you will get all kinds of interference which may or may not be noticable. This can have very poor effects on network performance. This is the reason for the two wiring standards. If you really could just pick any combination of colors that matched on both sides, there would be no reason for a standard.
Here is where I'm going with all this. If you have other cables, especially ones connected directly to your patch panels or switches that are not using a wireing standard, this is probably why your nonstandard cabling is the only one that will work...because when the two cables together go from one incorrectly wired cable to another, the interference is too great to even establish a connection. That particular cabling you came up with might arrange the pairs in such a way that the signal can still propogate down the line. I'd try replacing all the wiring from the workstation to the switch using a wiring standard to test the theory.
willbdman: I'm not sure I know how to test each wire within an Ethernet cable for integrity... could you give me a basic idea of how to do it?
dniverson: We have many of these existing cables (there's no spool or box of this cable), so I've just cut off the ends and re-crimped. The odd thing is, even when crimped "correctly" with the wiring scheme I laid out above, occasionally they still lose connectivity without any warning. I've tested the outlets and switches with known good ethernet cables/PCs, and they're fine. We do have regular 568A cables in places working with no issues (these are not made from the same cable that's giving me problems).
willbdman and dniverson: I will try a few cables at another location tonight, though I have tried them in many known working switches and devices, all no go.
DVation191 is right. The twists in the cable exist to avoid signal cancellation. My guess would be the cable your using wasn't manufactured properly. You might try a brand new cable. I buy mine here: http://www.cat5ecableguy.c
You stated that the cables are "in place", does that mean that they are running from a patch panel to wallplates? If so they may have been punched down at the wall plate in that order. I would look at the wall jack and make sure that end is done correctly. I do not believe that faulty twists would cause the cable to need to be terminated in one specific order and work
Save yourself alot of headache and get ahold of a cable tester, preferably one that can test a cable from one end to the other that's attached to a computer. This should give you an exact map of the final wiring pattern.
The wiring pattern you gave should actually work if both sides are crimped the same and the connection is going through a switch. Why? Because the switch will cross the transmit and receive cables which is what needs to happen. However the 568/B and 568/A standards should also work because that's all they are is standards. Get yourself a cable tester and if you can get one that measures attenuation and all that other stuff.
I'm stilling for documented proof...but this is a step in the right direction...
You can see how the 568A standard is layed out here:
http://www.ablecables.com.
Same with the 586B standard:
http://www.ablecables.com.
There is also a standard call USOC that uses CAT5/6 cable as well....if you take a look at the pin layout, they aren't using 568b OR 568a...they are using something else. Also notice the caption...
"Won't work for data"...the send and receive pairs NEED to be twisted together...if you use randon pin layouts (even if they are the same on both sides), you will have crosstalk and will severly limit the speed and distance you can get out of the cable, if they work at all.
http://www.ablecables.com.
Here we go...2nd to last question on the page...
http://www.lanshack.com/ca
Q: Is the order of the colors really that critical in a patch cable? As long as both ends of a straight through cable match, won't the cable work well regardless of the color order?
A: Of course the signals that travel over those wire pairs are color blind. That is to say that they could care less (if they could think) what color is on their insulation. However, the pairs are grouped inside of the cable and in the RJ-45 connector in a certain fashion. So each pair will react with each other in a unique way. This reaction does have an effect on the performance. The more important factor is the pairing. A circuit of either transmit and receive must travel over a pair that is twisted for maximum shielding from crosstalk.
"So each pair will react with each other in a unique way"
...The pairs are together to reduce crosstalk.
"This reaction does have an effect on the performance."
...Performance of cabling is measured in distance and speed (MHz), if you have decreased performance, you may not be able to send a signal far enough, resulting in a cable that doesn't work.
"The more important factor is the pairing."
...so while you can use the colors you want, you still need to use pairs of colors in the same fashion just as the 568A/B standard has.
"A circuit of either transmit and receive must travel over a pair that is twisted for maximum shielding from crosstalk."
...by using whatever color coding and order you want, you will not achieve this.
DVation191
In his pinout that he listed it says both pin 3 and pin 6 are green, what I said was that I naturally just assumed that he meant green/white one of the two which would still be correct because it the pinout is identical to the 568 standard. Maybe this will help
His Pinout 568B
pin 1 - blue Pin 1 White/Orange
pin 2 - blue/white Pin 2 Orange
pin 3 - green Pin 3 White/Green
pin 4 - orange Pin 4 Blue
pin 5 - orange/white Pin 5 White/Blue
pin 6 - green Pin 6 Green
pin 7 - brown Pin 7 White/Brown
pin 8 - brown/white Pin 8 Brown
Accourding to this the only thing that is different on his is they swapped the blue pair with the orange pair and swapped the solid wire for the striped wire in each pair. This should work, it's got to be something else that is causing the problem. I still say you should get a cable tester on it. Also reset your switches and change ports on some of your lines if you have available ones, I've had plenty of ports go bad on me. And if they're managed switches maybe the previous IT guys setup VLAN's that could explain some of it.
Signal testing can be done with a CAT5 Cable tester - these can be quite expensive though. I would agree with whats been said - if you are still having problems at other locations then the signal sent 'down the wire' is getting interrupted due to interference.
When a connection loses too many packets the transmission will fail - this can occur due to errors in cable or hardware. Have you tried running a continual ping test to see how many packets are lost, say over 5 minutes?
to do this open up a DOS prompt and ping another machine or router on your network
for example if pinging my router: (Ping 192.168.1.1 -t) the -t command makes the ping continual until stopped (by hitting Ctrl + C)
Responding to various comments:
- I have taken a few of the oddly-wired cables home, and tested them out - they seem to work fine.
- No VLANs set up on the switches. I reset them, tried a few different ports, same result.
- I will be purchasing a cable tester ASAP.... all of the cables that my associate and I crimped a while back (not from the same cable as the oddly-wired cables), we did have a cable tester available to us, and lo and behold, we've never had a problem with the cables we've crimped.
- I also plan on purchasing brand new boxes of cable.... but here's the kicker -- I checked yesterday, and some of this "problem cable" was also used to wire from many outlets to one of the patch panels in our server room. It appears to be punched down correctly both at the panel and all the outlets (using T568-A), but if we're having this many problems with regular patch cables from device to outlet, who knows what other kind of havoc it's causing?
Pic of my patch panel, all wires appear to be punched down correctly:
http://img.photobucket.com
DVation191: That's the thing, cables using the T568A standard *do* work, just not if they're made from the ethernet cable that I've been wrestling with.
From using these cables in various applications, especially when testing them out at home (using the original wiring scheme and then T568A and B ), I think it's safe to say that the cables are just screwy, and should be replaced ASAP.
Thanks to everyone who responded to this mystery of mine. :) I split points between DVation191, willbdman, and Newsboy, but everyone who commented had great suggestions. Thanks you again.
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by: willbdmanPosted on 2005-10-05 at 08:00:38ID: 15022443
The only way this would make sense is if BOTH ends of the cable were wired in the same way (so both ends meet - as you have already said you understand) or there is some problem with the actual cable.
Have you tried testing each wire within the cable for integrity?
Will