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I'm on a vSphere4 course at the momnet and we've just covered dvSwitches.

Our instructor is of the opinion that if you reboot your vCenter server, your dvSwitch goes "missing" for the duration of the reboot - so all your VMs lose network connectivity.

I don't think this is the case, as dvSwitches are a high-end bit of functionality, and this seems like a very big single point of failure - surely the configuration is managed by vCenter, but it's cached in some way by the hosts and they will continue to function - but changes cannot be made without the vCenter server being available?

Can anyone clarify what happens to a dvSwitch and the traffic passing over it when vCenter is rebooted?

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2 Answers 2

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That's simply not the case, they stay up, but they are in general a bit flakey to be honest.

Oh and no swearing on here please.

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I would question the quality of this course and the instructor's qualifications right there and then. Because that statement is definitely not true, and you, being a trainee and therefore not an expert, have no ability to tell if that was the only incorrect statement - maybe he's been feeding you crap all day long? At this moment, every single thing he told you should be suspect.

Now, emotions aside: if you look at the core functionality (ignore VUM, VDR, etc), vCenter is just a management tool. Everything that the host needs to function is stored in the host itself. Network, storage, or cluster configuration - you can find it all inside the host. Just look at the CLI utilities and what they're capable of when talking directly to the host, and you'll see how much can be accomplished without involving vCenter.

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I went on a VCP4 course where the instructor was seriously off on quite a few things - thank heavens for the internet :) –  Chopper3 Feb 17 '10 at 11:00

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