Thank you for posting at Wired Communities. What is the operating system installed and have you tried updating to the driver from Dell* as this is an onboard NIC on their system, it is recommended to use customized driver from the board vendor (as I understand you updated the BIOS and chipset already).
What is the brand and model of your switch?
The OS is Windows 7 (Enterprise). The driver version from Dell was 126.96.36.199. I had updated to this version from Dell a couple of weeks but this did not resolve the issue. I then found driver version 188.8.131.52 on the Intel site. I know it is not a huge difference in the versions but I updated it anyway. Again, this didn't resolve the issue.
As far as the switch goes, I do not have physical control over these devices, but I know for a fact they are Cisco switches, and in this case I "believe" the model number is 3750.
Thank you for the information. I did not encounter said issue but I managed to find this website which has similar issue (with different setup not exactly same as yours). And the switch they used is also 3750. You might want to refer to the information therein (Please note this website is provided here for your reference, Intel is not endorsing or has control over the website content since this is a third party website)
You may also contact Dell* support as these are onboard NIC on their system. It is recommended you contact the system manufacturer. Thank you.