Ok, what am I doing wrong?

[Tumble]

I have a "Realtek PCIe GBE Family Controller" NIC, which is built into the mainboard (Gigabyte E-43). I have the latest drivers I can find installed, a decent cable and a capable router/switch-a-ma-bob. The damned thing will not connect at 1gb/s. The router is a Virgin Media Superhub 2, and I built a new cable between it and my PC specifically for gigabit speed - which it achieves on my work computer no problem. The *really* interesting thing is, my PC won't even auto-negotiate the network speed. It only works if you force it to 100mb/s. I did get it to connect once at 1gb/s, but after a restart, that went away again and I haven't been able to replicate the feat since. Everything else on the wired network (which to fair is only the NAS) is connecting at 1gb/s according to the link lights on the back of the hub.

I'm thinking I should cut my losses and just get a discrete NIC, but there HAS to be some setting that I need to do that I don't know about... anyone got any ideas?

[KeyboardDemon]

It's a long shot but the only thing I can think of is the cable, you said it was a decent cable but haven't said whether it's Cat 5, Cat 5e or Cat 6. Which are you using?

[DanceswithUnix]

There doesn't need to be a setting, it should negotiate up if it can. Different speeds use the cable in different ways though, it isn't just a case of going faster. A few things I would try:

1/ Is there a network diagnostics section in your BIOS? Some have a network check built in, complete with simple time domain reflectometry test to say not just if the cable is OK but how far down the cable there is a problem if it isn't.

2/ Swap ports on the switch, that port may be damaged.

3/ Try a Linux live CD or DVD/flash drive. That should just work, and if you get the same results then use "su" in a command window to get root privs, then "tail -f /var/log/messages" to see what is going to the system logs, then unplug the network connection count to five and plug it back in again and see what it says.

I suspect you will be ordering a replacement cable and a network card though. Any PCIe card should do, for home use they are all much the same these days frankly.

[Tumble]

Righty o then.

The Cable
I built the cable myself, to replace the existing wiring which wasn't up to the job using solid core CAT6 wire (it has to go round some tight corners on it's way through the floor). I tested it with a proper network analyser wot I borrowed before and after I fed it through the wall - all ok. My work computer connects on that cable at a gigabit, so I know both the hub (which I have had replaced already) and the cable are good.

The hub/switch/router thingy
Call it what you want, but it's working fine - the NAS connects at 1 Gb/s plugged into the same port as my PC.

Linux CD
Can't be bothered with that. I suspect it'll have to be a new card.

Thanks for the replies!

[abaxas]

Couple of thoughts.

1) auto negotiation vs auto crossover flapping. Use a different straight through cable and fix it at one end. (more common than you think)
2) some networking gear simply wont talk to each other. There may be a standard but sometimes things don't get along. One of the old intel e100 (10/100) cards was terrible for this.

[Singh400]

It sounds like you are getting a lot of interference and it is auto-negotiating down.

I had a very similar and strange problem with my PC. Turns out on the switch, I had to leave a port in between plugged in ports, or the interference from two in use ports used to cause auto-negotiation to kick in and downgrade the connection.

[Tumble]

No interference - it won't auto-negotiate at all! Point's moot anyway. Got hold of a new card today, I'll play with it over the weekend if I get a chance

[watercooled]

As an extension to what abaxas said, how did you wire the cable? I.e. straight-through or x-over?

A Gigabit x-over cable technically needs the other pair swapping over too, though they're pretty much obsolete because of auto-negotiation.

I'm not too sure how a GigE port is supposed to handle an older-style x-over cable, but I guess it's possible some PHYs would act up when expected to negotiate GigE with them.

[Tumble]

No it's straight through - I wired it up according to the specs as well. Cross over wouldn't work as the current hardware can't distinguish between cross over & straight through automatically.

[watercooled]

To eliminate causes it would be helpful to test the system with a different cable and/or a different system on the same cable. It could just be a faulty onboard NIC - a few years ago I had a motherboard which would randomly refuse to accept a cable was attached.

[DanceswithUnix]

I'm not too sure how a GigE port is supposed to handle an older-style x-over cable, but I guess it's possible some PHYs would act up when expected to negotiate GigE with them.

I thought it didn't matter, given it runs each wire full duplex the concept of transmit and receive pairs is no longer relevant, they are just lanes which it has to work out the order of.

[watercooled]

But since a (10/100) crossover cable swaps pairs 2 and 3 (and ignores 1 and 4 as they're not used), I could see that causing negotiation problems as each side would be treating the pair as a different lane. I don't think there's a necessity to accommodate pair swaps in the spec. I'm not sure about specifically pair 2/3 swaps either.

[Tumble]

This is how I've wired the cable:


I believe that's to the 568b standard.

[watercooled]

Yeah sorry, was just going off on a bit of a tangent about how GigE might handle crossed cables.