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cmhtech techFlag for United States of America

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Weird PC Network Issue

Device is a custom built Systemax machine.

SPECS:

 Motherboard is Asus P5G4IT-M LX2/GB P4 Dual Core 775

OS is Windows 7 Professional 64Bit SP1

BIOS version 0408 (latest)

4GB DDR2 PC6400 Memory

250GB Samsung HDD SATA

The Computer is located at one of our WAN sites and sadly we run all 3com Networking gear (I’m trying to change that) The user using the machine states that every day it will drop its network connection for up to 15-20 minutes and then finally come back on at random intervals throughout the day.  It uses the onboard NIC.  Every time the error is the same “Network Cable Unplugged.”  Sometimes it will show that it’s not connected but still work just fine.  Originally it was tethered off of a 3com phone but I ran a new line to a different port on a completely different switch but with no luck.  So far this is what I have done and none of it has worked:

Tried new PCI NIC

Updated NIC Drivers

Made sure device had all latest updates

Flashed BIOS

Checked event log for any errors

Re-terminated the current cable on both ends

Untethered off of 3com phone and Ran New cable from new switch/port to PC

Reloaded PC with fresh install of Windows 7

Made sure power management was turned off for the NIC

Checked BIOS for any Power Management settings

Swapped power supplies, both 350Watt

Checked for any naming/DHCP conflicts

Tested Memory and HDD, both are fine

Checked for Speed/duplex issues

Here is the weird part.  When I bring the device back to our main location it never drops and the ping times are excellent.  But at the WAN site it drops about 1-2 packets every 50-60 pings and will disconnect at least once a day.  However, I have placed a spare HP device at the WAN site for the user and its pings never drop and user works with it just fine.   I am about to just give the user the spare to use permanently but I would really like to know what’s causing the issue for my own personal greed .
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David Atkin
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It's connecting at 100mbps full duplex.  I have tried purging the residual power and that didn't work either
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I have duplex statically set to Full and speed to 100mbps on all switchports that connect to any PC.  I am not blocking ICMP packets in any way within the LAN.  Only ICMP blocking is on my firewall for external connections only.  I tried placing a third switch over there just to make sure something weird wasn't happening with the first two but it still occurred.   I checked the switchports for any packet errors or drops and everything looked fine there as well. I also got up in the drop ceiling where I ran the new connection to make sure nothing was interfering with the run and all that is around are some old pipes.  No lights or anything else within 15 feet.  I am really at a loss for words at this issue...Like I said at this point I just gave the user the spare device but it's killing the Network Admin within me to know what the heck happened lol.
i would test with another nic card
I still think you missed have a duplex mismatch between switch to switch or switch to router connection. Also consider spanning tree on all switch to switch and switch to router connections.
Nobus I have already tried another NIC card, 2 now actually.

ChiefIT there are 2 switches and 1 Router at the WAN site.  I will double check those links on Monday to ensure there are no mismatches in between them.  Thanks.
Does it drop out If you ping the local host?

I.e. 127.0.0.1?
That's a good question, above.

Another thing to wonder about is IPsec configured on the machine. That can cause set of ping packets to not go through, and the next  1 or 2 sets to go through.

Also, a multihomed computer can do silly things like this.
Does not drop if I ping the local host (or atleast didn't after about 5000 pings so I stopped the pings), it is not multihomed and there is no IPsec configured anywhere on the machine or our network.  I also double checked for any duplex/speed mismatches and I couldn't find any.  All links between routers/switches are statically set to 100mbps full duplex.  Spanning-tree is running on all switches in the network.
Is the PC still working at your main site ok?

I wonder if it is worth installing wireshark on the PC and seeing what happens when it fails.
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