Dell Latitude D505 NIC and Switch issues

[hmcgillem]

I have a really odd problem occuring with a Dell Latitude D505 NIC and the network switches. Actually, I can't pinpoint what exactly is failing - I just have the symptoms.

First, the way I know there is a problem is when all workstations on one or both switches lose network access. When I look at the switch, either all of the lights are blinking fast and in sync, or if I'm lucky, only one of the lights is blinking fast indicating that there is a problem. If all of the lights are blinking fast, I have to replace the switch because the only way to reset it is to let it sit without power for a day or two. If only one light is blinking fast, I can remove the cable from that port and see what computer is causing the problem. It seems that there is only one workstation at the time causing the problem (one of our Dell Latitude D505 laptop users). I tried connected the laptop to a wireless router and the same thing happens as if it were wired to the network. It doesn't matter what brand of switch I'm using, the same thing will happen if I swap it out when I have problems.

I have tried a number of things.
- replace switches
- replace network cable
- update NIC drivers
- update BIOS
- repair connection
- set NIC speed instead of auto-negotiate

Any other thoughts? If you need more details, let me know.

 

[G0AOZ]

So it's just this one laptop causing the problem right? Does the problem still occur if you remove the power brick and just run the laptop on its own internal battery?

I've experienced similar problems which I put down to a dodgy and dangerous power supply unit. In fact, the PSU was putting a voltage on the computer's chassis which allowed sensitive users to actually feel a tingle!

ROGER - G0AOZ.

 

[hmcgillem]

Right now, it is just the one machine. However, another one of our laptop users caused the same problem with his laptop.

I have not tried removing the power brick.

 

[LawnBoy]

Are any of the switches you've used managed, if so what do their error logs show? Are the switches running STP?

You could be having a broadcast storm. Does that laptop use a docking station?

 

[hmcgillem]

One of the switches I was using was managed, but when this problem occurs, it crashes the switch so that I can't get into the logs and have to reset it.

The broadcast storm is what I've been thinking, but how do I track that? The laptop is not using a docking station.

 

[LawnBoy]

Storms are usually caused when a switch detects duplicate MAC addresses on different nodes. If the switch is running STP (spanning tree protocol) it will prevent this by disabling one of the duplicates.

Since the switches won't tell you, best bet is to use ethereal or some other network sniffer and see if you're experiencing floods of ARP requests.

 

[hmcgillem]

How can you have duplicate MAC addresses on different nodes?

Do I run ethereal on the suspect laptop or can I run it on my laptop and detect floods of ARP requests?

 

[LawnBoy]

ARP requests are broadcast so you will see them anywhere you look within that particular subnet.

How can you have duplicate MAC addresses on different nodes?

Several different ways, one of which is a flaky NIC in the pc. Another is a real honest-to-god duplicate address (it's not supposed to happen but it can, especially in the hands of a knowledgeable user).

 

[hmcgillem]

The problem is happening when connected to the network with either wired or wireless. And, it has happened on more than one laptop that is the exact same model/specs. Maybe it's the NIC causing the problem.

 

[LawnBoy]

When I say broadcast I don't mean via RF (wireless), I mean the packets are not switched and are presented to every node on that subnet.

It does seem unlikely that both adapters on a single laptop are messed up in the same way...

Is there any chance that wired and wireless are occuring at the same time? If someone has set the MAC the same on both adapters, it could explain what you're seeing.

On the laptop in question, pull up a DOS prompt and issue

ipconfig /all

This will show you the MAC address in use for each adapter that is active.

 

[hmcgillem]

I thought it might be some problem with both adapters so I disabled the wireless adapter. However, they each have different MAC addresses. I have even gone so far as to completely reconfigure the workstation. That doesn't resolve the issue either. And, I can't recreate the issue - I have to sit back and wait for it to crash the network again before I can do anything about it. Normally, it happens during normal business hours so I have to focus on getting everyone back online. It doesn't allow me to do much troubleshooting.

 

[LawnBoy]

I know what you mean, when your backbone has collapsed there's no time to figure out how.
Set up a sniffer on that subnet and just let it record continously. when the problem reoccurs, look at what the sniffer captured during that time frame. It's a hassle, but I don't have anything else to suggest.

 

[hmcgillem]

Thanks LawnBoy! That's what I've done - set up a sniffer. I guess I'm going to have to sit here and wait! Although, it has happened twice in a week, so maybe I won't have to wait that long.

 

[LawnBoy]

That's always fun, waiting for your network to collapse and knowing that it will "sometime".

You know it will only happen when your Board of Directors is on some critical videoconference to Taiwan...

 

[hmcgillem]

Well, I am scheduled to be on vacation ALL NEXT WEEK! So, it will probably happen then!

 

[AndrewTait]

Can I suggest you switch your cell phone off, and go away from home!!!!

=======================================
So often times it happens that we live our lives in chains
And we never even know we have the key

Ne auderis delere orbem rigidum meum
======================================

 

[hmcgillem]

I am planning on going away from home (several states away) and I have set up contact with a consultant in case anything comes up! I'm hoping for a very peaceful week - although, I usually ALWAYS get called! I guess that's part of the job when you're the IT man!