VMware 4.x NICs showing down after upgrade from 3.x

Dang. I spent a couple of days trying to figure out what was going on with an IBM xSeries server after upgrading a working system from 3.x to 4.1U1 , troubleshooting cables, adapters, firmwares only to find that it’s a ‘feature’ in the way 4.x deals with the specific type of Intel Gig NIC that I have installed in my estate which are the 82571EB Dual and Quad port adapters.

This KB article will help set you straight after I was pointed in the right direction by VMware support.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1010313

Hope this fixes you up quicker than the couple of days it took me to resign to the support case.