Crossover cable, not working (Kind of)

Hi,

I've recently made a crossover cable(30m) to connect between 2 laptops. I can't get it to work.

I have an IBM thinkpad, and my friend has a toshiba something or other. As far as I can see both NIC's are installed correctly with file and print sharing enabled etc.

Here is the strange part, I brought the cable into work to test it, I connected a desktop PC to one of the workers laptops and got a FULLY functional connection, with pinging and file transfer successful. So now I thought one of the NIC's in one of the laptops was faulty. I brought my laptop into work and low and behold I can't get a connection between my laptop and my desktop PC.

However, I connected the patch cable from the office into my laptop NIC and all of a sudden I have fully functional network access.

So here is the overview.

  1. Crossover between myself and my friends laptops (FAILURE)
  2. Crossover between computer desktop and work laptop (SUCCESS)
  3. Crossover between computer desktop and my laptop (FAILURE)
  4. Patch cable from work network into my laptop (SUCCESS)

What the hell is going on ?

My thinkpad is a 1999. Is there a possibility that my workmates new laptop is able to detect a bad crossover cable wiring and re-transmit the signals on different pairs to get a successful network connection ? Confused,

Ronan Walsh.

Reply to
Jimmythekey
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I don't think it's a patch cable, but the cable might be faulty (might have followed a dodgy diagram). I'm re-crimping it now, so I'll see how that goes.

Thanks.

Ronan.

Reply to
Jimmythekey

I don't think it's a patch cable, but the cable might be faulty (might have followed a dodgy diagram). I'm re-crimping it now, so I'll see how that goes.

Thanks.

Ronan.

Reply to
Jimmythekey

Ok guys, here is where it gets weird.

I got a small patch lead (Straight through) and connected it from my desktop computer straight to my laptop. I got a connection and could ping. Is that not a bit weird to anyone else ?

I then thought, I'll just re-wire my crossover cable to a patch lead and I'll be sorted ! However, I re-wired my 30m crossover cable to a

30m patch and when I connected NOTHING happens. Damn this is annoying me. I even got a multi-meter and checked pin for pin that they were all getting a signal.

I don't think it's the length of the cable as it did work when connected from desktop computer to another work laptop. This is really confusing ... help.

Ronan.

Reply to
Jimmythekey

Yes, it is confusing. If the workmates new laptop has gigabit, there's an excellent chance it has auto-MDI and can correct for crossover. You may well have a straight patch cable.

Check by looking carefully through the plastic at pin 2 (2nd from left, tab down, plug pointing away) on both ends. It should be different for a proper crossover cable (orange vs green). If you have two oranges, you have a regular patch cable.

-- Robert

Reply to
Robert Redelmeier

My first bet, would be the cable. Get another one and see if it works. Did you wire it correctly? Check EIA/TIA 568A or B for details.

Reply to
James Knott

More than likely you've got a mis-wired cable. Check to make sure it's wired to spec.

Reply to
James Knott

I used this page

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the source of my diagram.

Bear in mind i've never had any problem making cables before this. Bah I'm stumped , oh well.

Ronan.

Reply to
Jimmythekey

Egads! T-568A or T-568B? What do you consider a "crossover"?

If you don't know what that question means, it is vastly improbable that you can make a cable without split pairs. Such a faulty cable might work over short distances, but will not over long distances even though you will get link lights.

There are 40,320 ways of wiring a cable "straight-thru". Only 1,152 work for 10/100. 384 for gigabit. None are intuitive. Only two are standards.

Beware of newbies with crimpers. Even pros normally buy.

-- Robert

Reply to
Robert Redelmeier

This is correct if you read carefully and look at the diagrams very closely and realize the plug tab is down.

Also, you need to make sure you are using the correct plugs for your cable type (stranded vs solid). Then you have to crimp with the correct force.

-- Robert

Reply to
Robert Redelmeier

What diagram?

Here's how I do it. Colors are body-stripe. If you're looking down at the gold connectors imbedded in the RJ-45 connector with the cable in your hand, pin 1 is on the left (or just look at a factory made EIA-568B cable).

EIA-568B Cross Over end white-orange (1) (1) white-green orange-white (2) C (2) green-white white-green (3) A (3) white-orange blue-white (4) B (4) white-brown white-blue (5) L (5) brown green-white (6) E (6) orange white-brown (7) (7) blue brown-white (8) (8) white-blue

The left side is standard official politically correct EIA-568B color coding. The right side is all 4 pairs crossed over. Many cross over cables only cross two pairs leaving the other two straight through. That's fine for 10baseT and 100baseTX, but does NOT work with

1000baseTX, which uses all 4 pairs.
Reply to
Jeff Liebermann

Reply to
Justin Time

I must be missing something here. Google is not doing a very good job of posting the comments to a message.

My response was to use the ABSOLUTE best way to create a cross-over as posted by John Lundgren a couple of years back. It takes a few parts, but it never fails.

Take a short piece of cable, two jacks, a surface mount box and a permanent marker. Wire one of the jacks to the T568A pattern, the other to the T568B pattern. Place the two jacks in the surface mount box and then mark the box with a large X on the top. Use two standard patch cords. There never is the problem of not knowing if you have a standard or cross-over patch cord.

Rodgers Platt

Reply to
Justin Time

What I did, was take a cheap ($2) line coupler, and rewire it to be a crossover. Works fine so far.

Reply to
James Knott

I carry a 2 ft xover cable and a CAT5 coupler in the tool bag. (I reserve red color for them.) With that I can make any CAT 5 connection, anywhere an Xover, or prove that an existing cable is or is not xover.

When I find a permenant cable that is wired xover I have the urge to chop the ends off.

Reply to
Al Dykes

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