Two days ago, I upgraded our vCenter server to version 4 update 1. For reference, vSphere reports build 208111.
About 24 hours after the upgrade (which, probably coincidentally, is the timeout on our dhcp leases) most of our VMs on dhcp stopped acquiring addresses. This affects both linux (using dhclient) and windows boxes. At first we thought there was an issue with our dhcp server but we were able to confirm that it was working properly with a few physical boxes.
I was wracking my brain and looking at the configuration of the few machines which were still working and comparing that to our non working machines. Then I noticed that none of the non working machines had a checkbox next to "Connected" on their network adapter settings page. So obviously, I checked the box and saved the settings. No good. It just goes right back to unchecked as soon as I reopen the settings. Then I tried powering off the machine and powering it back up and that still didn't fix it.
Here, I was stumped for awhile but then noticed that the adapter type on one of the working machines was set to "E1000" where the type on the non working machines was "flexible". I thought that was odd so I powered down one machine and removed it's existing adapter. I added an "E1000" type adapter and booted it up and sure enough, dhclient got an ip address immediatley. Thinking I solved the problem I brought up another machine and did the same thing. No good, still not getting a dhcp address and when I look, the adapter isn't connected. Crap.
Finally, I decided to just delete one of the machines and clone it again from the template. That failed for the first machine I tried it on, still not connecting the adapter. The second clone from template worked! But then the third failed again.
I have no idea what's causing some adapters NOT to connect and some work fine. This issue appeared after we updated to vCenter 4 update 1 so I'm fairly certain it's related to something in that.
If anyone has any ideas, I would be glad to hear them. Configuration info can be supplied if needed.
