VMWare ESX 4.1 to 4.1 U1 Upgrade Network Card Gotcha!


We recently upgraded our ESX hosts to ESX 4.1 U1, upon applying the 4.1 U1 update and then rebooting the server we found that the network adapters had all changed themselves to 1000Mbit Full Duplex. However we had everything set at “Auto Negotiate.”

The fix was simple, change this back to “Auto” on the ESX host, down and up the port on switch just be sure and check the speed and duplex reported on ESX and the switch are correct and your golden.

Just remember to move an (unimportant) VM to test networking before moving those Exchange VMs!