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NIC Lighting Up Switch While Off

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owensdj

Golden Member
This network with a single 24-port gigabit switch started having major network problems. The two servers couldn't even ping each other at times. I powered off all of the Windows client machines and physically unplugged the Internet router and wireless access point, but I saw *3* devices lighting up on the switch, instead of just the 2 servers. The two servers still couldn't ping each other, but as soon as I disconnected the client machine from the switch, everything worked fine after that.

My question is what could be happening with that client machine that's causing it to interfere with the rest of the network? Is a bad built-in NIC causing a broadcast storm?
 
Is the client machine similar in specs to the other client machines? Are you using onboard NIC? What brand is the NIC? Do you have Wake-On-LAN enabled? Have you tried swapping the client machine with another one? Changing the cable? Changing the port that the cable and client machine is connected to on the switch?
 
her209, thanks for the reply. No the problem client machine isn't the same as the other clients on the network. It's older. Yes it's using the on-board NIC. I'm not sure about the onboard NIC brand.

We're going to pick up a better cable and try that. We recently rewired the network from 100Mbit to gigabit, but that computer's patch cable wasn't changed from Cat 5 to Cat 6 like it should have been.
 
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owensdj said:
her209, thanks for the reply. No the problem client machine isn't the same as the other clients on the network. It's older. Yes it's using the on-board NIC. I'm not sure about the onboard NIC brand.

We're going to pick up a better cable and try that. We recently rewired the network from 100Mbit to gigabyte, but that computer's patch cable wasn't changed from Cat 5 to Cat 6 like it should have been.
Click to expand...
Try moving the computer to another connection (i.e., another office or cubicle) and see if the problem goes away.
 
Sounds like a loop. Make sure the wired and wireless aren't bridged. But if the client is turned off and you still have link light on switch, given that the wiring was changed, it's possible you have cabled a loop. Does the switch run spanning-tree?
 
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spidey07, I'm not sure if the switch runs spanning-tree. It's a HP ProCurve 1400-24G (J9078A) unmanaged switch. I don't see anything about STP in the features or specs.

Could this be caused by a client machine connecting to the network using both its wired and wireless?

How would I find a loop if it got cabled like that?
 
If the wireless and wired card are bridged that creates a loop. But that still should only happen when the problem client is up. If you want to check for a loop use wireshark and if all you see is a steady stream of brodcasts filling up the link, that's a clear indication of a bridging loop.
 
I noticed some of my realtek onboard nics cause a link light even though the machine is turned off (but still plugged in).
Switch is a SOHO trendnet gigabit 8-port, the one with the metal casing, but before they introduced their "green" switches.
 
For anyone who may be following this thread, I think the problem was that the computer was still using an old Cat 5 patch cable on the new Cat 6 wiring.
 
VirtualLarry said:
I noticed some of my realtek onboard nics cause a link light even though the machine is turned off (but still plugged in).
Switch is a SOHO trendnet gigabit 8-port, the one with the metal casing, but before they introduced their "green" switches.
Click to expand...

Many NICs support WOL, which essentially leaves the NIC in a powered on state so that it can receive a "Magic packet" which will tell the system to power on. A link being lit, in that context, shouldn't raise any flags.
 
mvbighead I think all of the computers on this network have a NIC that supports WOL, but this problem port was the only one lit up. By lit up I mean not only the link light number on the switch but also the LED for that port that indicates that the port is in gigabit mode.
 
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