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How can I test a NIC to make sure it's not putting out bad packets?

B

BZeto

Platinum Member
Is that even a possibility?

We have a divided room with 12 machines and a Dell Powerconnect switch on each side. Side A's switch has been replaced twice already and is showing signs of failing again. I'd say the switch will last 2-3 months before it goes out. When it happens the computers have no network connection at all, won't even get an IP address.

I was looking at the lights on the switch today with all of the machines on and other than the uplink there was one port light flashing activity (the other 11 were solid lights). I rebooted this computer and all of the sudden the other machines start to work. Now it could be a coincidence, but what are the chances this machine spazzing out the switch or something? Are there any tests I could run?
 
You can use Wireshark to get a packet capture on the PC that is connected to the "busy" port and see what kind of traffic it is putting out.

Are you saying that when that PC is on, none of the other PCs connect to the switch can communicate; but when that PC is off, they work fine?
 
It's highly unlikely that a PC/NIC could send any frames or packets that would physically harm the switch, if not darn impossible. What is more likely is you have some kind of cabling/ground problem and that is damaging the switch and ports, for example more voltage on the cable.
 
You have a grounding / induction / leakage issue someplace in the room. Are you using shielded cables? You shouldn't be. Are the cables run with or through florescent light ballasts or near motors or the misc starting controllers? You may be inducing a high voltage on the cables.

Check for voltage from ground to neutral in the outlet. Perfect is 0V but it won't happen. 2-5 volt AC is generally ok, any more than that and your running in to trouble. Check the A/C voltage while the room is up. Another common issue is voltage sag which can induce currents on data wires (esp shields.)
 
Originally posted by: seepy83

Are you saying that when that PC is on, none of the other PCs connect to the switch can communicate; but when that PC is off, they work fine?
Click to expand...

No. The switches seem to work fine with all PC's for a couple months before anything happens. This location is in another city, so I finally made a trip to look at it first-hand rather than guess over the phone. I have a new switch on its way but I wanted to check the current situation out first. That's when I noticed the single PC link activity. Now the people at this place said they have rebooted the switch several times with no luck. I just find it odd that I walk in, reboot that specific PC and everything is working again...

Originally posted by: spidey07
It's highly unlikely that a PC/NIC could send any frames or packets that would physically harm the switch, if not darn impossible. What is more likely is you have some kind of cabling/ground problem and that is damaging the switch and ports, for example more voltage on the cable.
Click to expand...

I will see if I can find a volt meter somewhere.


Originally posted by: imagoon
You have a grounding / induction / leakage issue someplace in the room. Are you using shielded cables? You shouldn't be. Are the cables run with or through florescent light ballasts or near motors or the misc starting controllers? You may be inducing a high voltage on the cables.

Check for voltage from ground to neutral in the outlet. Perfect is 0V but it won't happen. 2-5 volt AC is generally ok, any more than that and your running in to trouble. Check the A/C voltage while the room is up. Another common issue is voltage sag which can induce currents on data wires (esp shields.)
Click to expand...

No shielded cables. The cables are simply run from the PC's along the ground to the switch which is also sitting on the floor. The room has the in-the-floor power outlets and network jacks.


 
Originally posted by: spidey07
It's highly unlikely that a PC/NIC could send any frames or packets that would physically harm the switch, if not darn impossible. What is more likely is you have some kind of cabling/ground problem and that is damaging the switch and ports, for example more voltage on the cable.
Click to expand...

I agree, and would add possible static electricity issues.

A blast of static that you can barely feel is tens of thousands of volts ... more than enough to kill a poorly designed switching module. Extreme Networks had this problem in some of their early switches ... even a small zap would wipe out a port group (they used four ports per transceiver module).

Start implementing static protection methods (straps & booties).

Also get that stuff racked! You have no good drain for any power or noise issues.
 
Originally posted by: ScottMac
A blast of static that you can barely feel is tens of thousands of volts ... more than enough to kill a poorly designed switching module.
Click to expand...
My first 10Base-T switch (9-port) had one port connected to a CAT5 cable that ran 150 feet across my roof (yeah, I know....). Every six months or so I'd lose that port and had to connect the CAT5 cable to a "new" port. The switch on the other end of the exterior cable suffered no damage.

Eventually, I switched to a Linksys 100Base-T switch and never lost a port again. That same 10Base-T switch worked fine for ten more years as long as I didn't try using the "burned" ports. It only stopped being used because it had too-few remaining ports.
 
Originally posted by: RebateMonger

My first 10Base-T switch (9-port) had one port connected to a CAT5 cable that ran 150 feet across my roof (yeah, I know....). Every six months or so I'd lose that port and had to connect the CAT5 cable to a "new" port. The switch on the other end of the exterior cable suffered no damage.
Click to expand...

Rednecks have cars on blocks in their yard.

Computer geeks have CAT5 cables running across their roof!

:laugh:

 
Originally posted by: Engineer
Originally posted by: RebateMonger

My first 10Base-T switch (9-port) had one port connected to a CAT5 cable that ran 150 feet across my roof (yeah, I know....). Every six months or so I'd lose that port and had to connect the CAT5 cable to a "new" port. The switch on the other end of the exterior cable suffered no damage.
Click to expand...

Rednecks have cars on blocks in their yard.

Computer geeks have CAT5 cables running across their roof!

:laugh:
Click to expand...

What are you when you have both? :laugh:
 
Originally posted by: Gillbot
Originally posted by: Engineer
Rednecks have cars on blocks in their yard.

Computer geeks have CAT5 cables running across their roof!
Click to expand...
What are you when you have both? :laugh:
Click to expand...
Probably the guy with a plastic swimming pool liner in his truck bed.
 
Originally posted by: RebateMonger
Originally posted by: Gillbot
Originally posted by: Engineer
Rednecks have cars on blocks in their yard.

Computer geeks have CAT5 cables running across their roof!
Click to expand...
What are you when you have both? :laugh:
Click to expand...
Probably the guy with a plastic swimming pool liner in his truck bed.
Click to expand...

And a Darwin Award candidate in the making. Congratulations!
 
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