Electricity, Grounding and Eth

Question

I'm having an intermittent problem in my server ethernet card. After reboot, the ethernet card sometimes didn't go up automatically. Running ifup -a after reboot ensures that the eth is up, regardless of it's previous status. Is this a problem that can be caused by electricity issues (grounding, fluctuation, etc)?

Answer 1

Ethernet wires themselves use a balanced transmission, no wires in the wire package itself should be grounded unless you're doing power over ethernet.

What exactly does "ifconfig eth0" (or whatever) report? Does it report loss of signal, or that it just isn't marked as up?

If it just isn't up, there may be a race condition on your system software, or the device is appearing too late in the boot cycle. You could stick a "sleep 5" or something in the bootup script that configures the net (or a phase before it) and see what happens.

Is the switch it plugs into managed? If so, what does it say?

I generally advise against locking ports down these days, although I used to recommend it on older switches, around the baystack era. These days I would let the magic happen as it generally happens correctly.

Did you try another cable btw, or switch, switch port, switch manufacturer, or ethernet card?

Answer 2

Sometimes, but in my experience the more common case is that the network card itself and the switch-port it is plugged in to can't finish their autonegotiation in time for the kernel. By forcing it later they've finished their negotiation-tango. Happily, this kind of thing is easy to check for, just hard-code the switch port to something (100-full) and see if it goes away.