Can a faulty NIC crash a network?

[a_unique_person]

We had a severe network outage at work, with our **** old 3COM switches blinking like a xmas tree. After it was 'fixed' and completely rewired, I noticed they had forgotten to wire in one of the servers. This server had a NIC that had gone dead once, and refused to connect once the NIC was wired into the switch. On rebooting, it just hung. I moved the cable to the other NIC, and it booted and ran fine.

What did happen was that over the night, the network performance degraded, after working fine during the evening. By morning, the network was dropping packets. By 8.30am, it just completely died.

My guess is it's failing NIC flooding the network with junk. Anyone agree?

[pingnak]

Yes, it's possible for a faulty NIC or switch to take a network down.

[ElMondoHummus]

Absolutely it's possible. I've seen a faulty NIC completely disrupt a subsection of a network before. When plugged in, everything sharing that switch got nothing at all. When I was involved with the troubleshooting, I figured the problem was what the OPer was saying: A bad NIC causing a huge packet blizzard which in turn induced a local denial of service to everything attached to that switch. But I was told that it was the opposite, that there was simply no signal traffic whatsoever while that computer was attached. Weird. I don't remember what my university's networking team did to determine that, but that's what I remember being told about it. The theory was that the bad ethernet adapter was somehow shorting things out.

A simple NIC replacement got rid of the problem. So the answer to the OP's question is a very firm yes, from personal experience.

[a_unique_person]

We had an incident at work. I plugged in a new switch, daisy chained it to the rest, and moved some cables from the old switch to the new one. The new one being Gigabit, hence the change. When I left, the network was fine, with people working from it. About 6.00am, dropouts started, 8.30am, the network pretty well died. They tried to blame me for the problem, with a mistake being made with the cabling. However, if I had introduced a loop or similar, the network would have died instantly, not taken about 12 hours to gradually degrage, IMHO.

The fact that the server with the faulty NIC was not wired in when the problem was resolved, confirms my suspicion.

[ElMondoHummus]

Yes, I fully agree with you. Any cabling or setup mistake would've manifested immediately. Whereas a gradual degradation could indeed be due to a network card going bad.

[ElMondoHummus]

Hey, waitaminute! I do this for a living at work, then go home and do this to relax??

What the hell's the matter with me?? :confused::boggled: I'm getting out of this subforum, right now!!! :D

[leonAzul]

A failing NIC is possible.
A rootkit is also possible.

Please, check for either!

[a_unique_person]

Hey, waitaminute! I do this for a living at work, then go home and do this to relax??

What the hell's the matter with me?? :confused::boggled: I'm getting out of this subforum, right now!!! :D

My apologies. They have been giving me hell over this, so the expert advice is much appreciated.