vMotion vSwitch Requirements Understanding & Clarity

[nzmarkc]

Can you have VMs attached to an INTERNAL only vswitch and still vMotion the VMs??

I am getting conflicting information as to the ability to vmotion VMs when they are attached to an internal only vswitch. What I have found so far is:

The 'Mastering VMWare vSphere 4 by Scott Lowe states on Pg438 "The virtual machine must not be connected to an internal-only virtual switch." As does his (et al) 'VMware vSphere 4 Administration: Instant Reference' book on pg248 state "The virtual machine must not be connected to an internal-only virtual switch (that is, a virtual switch without any connectivity to the physical network)."

BUT...

A colleague of mine has VMs attached to internal only vswitches and he _can_ vmotion the VMs. In this case, there is a virtual router connecting the vswitches so any traffic between the VMs on internal vswitches must be routed. But there are no pNICs on any of these vswitches.

Also, I cannot find anything in the offical VMWare documents: www.vmware.com/files/pdf/vmotion_info_guide.pdf [VI3], www.vmware.com/pdf/vsphere4/r40/vsp_40_admin_guide.pdf [vSphere4], which states that the vmotion requirements include the "no internal only vswitches".

So can anyone point me in the right direction please?

Thanks!

Mark

[logiboy123]

You cannot perform a live vMotion of a VM that has a vNIC, attached to an internal only switch with no pNICs assigned.

You can cold migrate a VM that has an internal only switch attached, but you will have problem's with the VM unless a switch is available with the same named port group. on the destination host.

How can a VM router with no pNIC allow traffic to flow between two physical hosts? At some point there needs to be a physical connection between two hosts in order for traffic to pass between them.

Regards,

Paul

[AndreTheGiant]

Some check are perform before a vMotion.

But if you have mistmatching network configuration (for example different portgroup label) or isolated vNIC, then vMotion will still work... but the final result is the virtual networking will not work.

Andre

[nzmarkc]

     Thank you Paul and Andre, but this doesn't quite answer what I was after. I understand the vswitch and port group naming requirements (i.e. being the same from source to dest). But ...

1. Where does it say in the VMWare documentation that you cannot vMotion a VM attached to an internal-only vSwitch?

2. There are plenty of situations where a VM might be connected to an internal-only vswitch.

     The image above shows an actual situation. The VMs 1 to 3 are only attached to internal-only vswitches - and yet I am told they can vmotion. Indeed, why shouldn't they be able to vmotion to another host ready with the appropriate setup?

     So Paul, in answer to your question "How can a VM router with no pNIC allow traffic to flow between two physical hosts? At some point there needs to be a physical connection between two hosts in order for traffic to pass between them." The above image shows what you have asked. There is technically a physical pathway to another Host, but this scenario has VMs on internal-only switches. So maybe that is questions three!

3. What is the correct definition of an "internal-only" vswitch?

Thanks again!

Mark

[AndreTheGiant]

1. There isn't... in fact you can do vMotion... but a functional requirement (in order to make VM work) is have correct portgroup naming.

3. There isn't a definition... The correct term could be "isolated vSwitch" -> without ANY uplink (aka pNIC).

It isn't a technical limitation... you can move the VM... but if portgroup name mistmatch you will have the vNIC disconntected...

Andre