I've got a 10m network cable that I use to connect either one of my laptops - an HP Omnibook and an IBM Thinkpad - to a router. Now, when I connect the HP Omnibook, everything is fine: the little green link integrity light is on, I can see the internet and the other computers on my network, and I'm happy. However, when I connect the IBM Thinkpad using this same cable, the link integrity light stays resolutely off, and I can't see anything on the network. If I then bring the IBM Thinkpad physically closer to the router and connect it using a 1m cable instead, the link light comes on and everything works.

So, my questions are: Is that weird or what? Why would that be? And how can I fix it, if at all?

How old is the cable? Perhaps the IBM expects all 8 pins to be wired correclty and the HP only needs four. Does the IBM hava a giga-bit card?

Another possiblity would be the HP is autosensing a crossover cable?

Try other cables. Use a cable tester to test the 10m cable or try it with other machines.

Just bought it yesterday.

Is that something I can check visually? (I'm a bit of a networking noob.)

I'm pretty certain it hasn't.

Eh? Would connecting the laptop to a router with a crossover cable actually work, anyway?

Well, I know the cable must be sort of OK because it works with the HP laptop. If it turned out not to work with another machine, what would I have learned?

The tolerances between the connector of the cable and laptop might be loose enough that it isn't making a good connection.

I would try another cable.

The problem is probably not with the cable, rather it might be the jack on your PC. I have seen this happen many times before. Take a close look in the jack, look for pins 1&2 to be slightly pushed down (slightly bent), or lower than the rest.

This typically happens when someone plugs a phone cable (4position plug) into a LAN jack. The 4position plugs do not have recesses for pins 12,78 and they can be bent down slightly when plugged in,and cause a poor/incomplete connection when a 8position plug is inserted.

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I'll have a look, but if that's the problem, wouldn't it be a problem with every cable I connect to the Thinkpad? (The shorter patch cable and a 2m crossover cable both work OK.) If not, would using the other end of the 10m cable in the Thinkpad solve the problem, perhaps? Well, at least I have some experiments to try later!

OK, problem apparently solved. I just turned the 10m cable round (i.e. put the plug that used to be in the router into the Thinkpad, and vice versa), and the link integrity light is shining happily.

Can't say I really understand why it's working now, but I won't complain!