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configuring Vswitches for Vmotion

Posted on 2016-11-01
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configuring Vswitches for Vmotion

When configuring Vmotion , do we need to have Vmkernel Port(Vmotion) as well as VM port group on the same Vswitch with physical NICs ?

I have seen some set up where they have 2 Vswitches,:

Vswitch1 with 2 Physical Nics and Vmkernel for vMotion is on Vswitch1

Vswitch2 with no adapters(no physical Nics) and has VM port Group.

I am not sure if the vMotion can occur that way , because the vswitch2 does not have Physical Nics.
Can someone give an insight on that ?

Thank you
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Question by:jskfan
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by:rauenpc
ID: 41868436
You just need to have a vmKernel, mark it for vMotion, and give it appropriate ip address and vlan tag if applicable. Whatever vSwitch the vMotion vmKernel resides must have a physical nic available, and of course the actual switches that the servers are connected to must be configured.

if the vMotion vmKernel is on a vSwitch with no physical adapters, it will not work as it has not physical connection available for use.

Make sure that things like the same vlan, vlan tagging, and correct IP addressing are used. Also, any given VM being vMotion'd will need the same port groups available (by name) on each host participating in the vMotion.
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LVL 117
ID: 41868457
Vswitch1 with 2 Physical Nics and Vmkernel for vMotion is on Vswitch1

That is correct and fine.

A vMotion portgroup is a VMKernel Portgroup with an IP Address which is Tagged for use with vMotion.

Hosts must be able to communicate with each other via IP Addresses, for a vMotion to complete successfully.

Try a vMotion between hosts, if it cannot connect to another Host's vMotion it will fail the validity check.

always test vMotion using VMKPING, if you can VMKPING another Hosts IP Address (VMKernel selected for vMotion) it should succeed.
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Author Comment

by:jskfan
ID: 41868502
What I was trying to understand if the vmotion can occur while:
Vswitch2 with no adapters(no physical Nics)  has VM(Virtual machines) port Group.

how do VMs migrate (vmotion) if the vswitch2 they are on does not have physical Nics ?
Even though Vswitch1 looks properly set up as I mentioned above
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Expert Comment

by:rauenpc
ID: 41868552
The VM's themselves essentially have no part of the vMotion action. It is all up to vCenter and the hosts themselves to coordinate and move the VM. It's the hosts that communicate with each other using the vMotion vmKernel, not the VM itself. As long as the destination host has the same port groups (whether or not backed by a physical nic), that is all that matters, along with a list of other resource checks and verifications. Now the functionality of that VM is a different story. A port group with no physical nic limits the VM to communicating internal to the host at best, but the VM can still be moved.
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LVL 117
ID: 41868584
What I was trying to understand if the vmotion can occur while:
Vswitch2 with no adapters(no physical Nics)  has VM(Virtual machines) port Group.

how do VMs migrate (vmotion) if the vswitch2 they are on does not have physical Nics ?
Even though Vswitch1 looks properly set up as I mentioned above

What you have to remember is that vSphere will do a validity check to see if the destination host, where the VM is going to be moved to HAS THE SAME VM Portgroup Label, otherwise it cannot move.

The VM (bit which is resident in the host memory) is what is sent down the vMotion Portgroup to the other Host.

it has nothing to do with the VM Network portgroup it's attached to.

The VM is just an object hosted on the host, and it's the memory contents which are moved.

vMotion is a little dumb, it does not actually check to see if the correct networking is in place and working....

so it is possible to move a VM to another host, and when it's on that host, it can no longer communicate because networking on the host is incorrectly setup.
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Author Comment

by:jskfan
ID: 41868865
I selected different ESX host now:

when I select ESX host/Configuration/Networking:

I  seen  Vswitch1 with 2 phsyical Nics, all it has is 2 Vmkernel ports (vmotion and
Management Network)

Vswitch2 with 2 Physical Nics , it has 2 Virtual Machine Port Groups

Vswitch3 with No physical adapters, it also has 2 Virtual Machine Port Groups

 

How does Vswitch3 communicate with Vswitch1 and 2 ? is that all handled by the ESX host they are on ?

If I remove physical NICs from Vswitch2 will that work too ?
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Expert Comment

by:rauenpc
ID: 41868889
A 'vSwitch' is more or less like a container object. It contains vmKernels and port groups, and there are rules and policies that get applied. These rules and policies really only say how traffic is to be treated, and which physical nics to use for outbound traffic, and how to register MAC addresses to the physical switch (which affects the return inbound traffic). These are not truly software switches; they do not have much in terms of routing/switch ability. vSwitchX has no means of 'communicating' with vSwitchY.
Removing physical nics on a given vSwitch will stop any VM's that are part of a port group on the vSwitch from actually communicating across the physical network, since the rules/policies don't give any physical access outside the host.
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Author Comment

by:jskfan
ID: 41868922
I will have to add snapshots for clarity purposes when I get a chance
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LVL 117
ID: 41868976
Snapshots ? you mean screenshots ?
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LVL 117
ID: 41869032
I  seen  Vswitch1 with 2 phsyical Nics, all it has is 2 Vmkernel ports (vmotion and
Management Network)

Vswitch2 with 2 Physical Nics , it has 2 Virtual Machine Port Groups

Vswitch3 with No physical adapters, it also has 2 Virtual Machine Port Groups

These are just like physical switches, in the physical world, they are ALL ISOLATED from each other. Unless you connect them with a network cable. Traffic does not leak via the host!

How does Vswitch3 communicate with Vswitch1 and 2 ? is that all handled by the ESX host they are on ?

they do not communicate with each other

If I remove physical NICs from Vswitch2 will that work too ?

if we are discussing vMotion, yes communication can ONLY HAPPEN via an IP Address on the VMKernel Portgroup TAGGED as vMotion.

So yes it will still work.

vMotion communication has go nothing to do with Virtual Machine Port Groups
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Author Comment

by:jskfan
ID: 41869074
Vswitch3 with No physical adapters, it also has 2 Virtual Machine Port Groups
Can those VMs on vswitch3 communicate with VMs on vswitch1 and Vswitch2 as well as other VMs outside ESX host they are on. Assuming ESX host they are on can talk to other ESX hosts in the Network
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LVL 117
ID: 41869086
VMs on vSwitch3 CAN ONLY COMMUNICATE WITH VMs on vSwitch3.

So Answer NO.

There is no internal communication between vSwitchs.

Traffic cannot leave the vSwitch3, because there are NO UPLINKS.

Again, I would encourage you to experiment! and prove this for yourself, so you can see it happening.
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Author Comment

by:jskfan
ID: 41869743
Andrew,
That's what I thought too..
VMs on vSwitch3 CAN ONLY COMMUNICATE WITH VMs on vSwitch3.

What about vmotion of VMs on Vswitch3? I do not think they can be vmotioned either.
Correct?
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LVL 117
ID: 41869959
Again, vMotion validity checker, checks whether a vMotion can happen before it's attempted. You cannot proceed to complete a vMotion if the validity checker fails.

Okay, see if you can follow this example.

A Virtual Machine called Windows, on Host A, connected to a virtual machine portgroup called DING DONG on vSwitch4, it could be on any vSwitch, is selected for vMotion to Host B.

Host B DOES NOT HAVE any virtual machine portgroup labelled DING DONG.

vMotion WILL NOT COMMENCE. and you'll get an error message see here

vMotion.jpg
Assuming that Host A and Host B have the correct vMotion communication channels established and setup in networking.

So it's got nothing to do with vSwitches, but VIRTUAL MACHINE PORTGROUPS

So in answer to your question, it depends yes or no....

do you have the same labelled VIRTUAL MACHINE PORTGROUPS on a vSwitch on the host you want to vMotion to?

If yes - then you can vMotion.

if no - then you cannot vMotion.

Solution

Create a new Labelled virtual machine portgroup and validiting checker passes, and you'll be able to vMotion.
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Author Comment

by:jskfan
ID: 41870206
Managed to make screenshots.
well, the VMs on the bottom switch (has no uplinks).
can they be vmotioned if all vmotion requirement are met except of the (vswitch that they are on and does not have uplinks)
scsc
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LVL 117
ID: 41870320
did you read my last post, YES and NO.

Does the destination host, have the same virtual machine portgroup labels as the  source host ?

If Answer is YES - then YES.

if Answer is NO - then NO.
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Author Comment

by:jskfan
ID: 41870669
Andrew,


assuming Everything has passed Vmotion validity checker.

Can you explain how VMs on the lower vswitch(without Uplinks) can be vmotioned to another ESX Host ?
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Accepted Solution

by:
Andrew Hancock (VMware vExpert / EE MVE) earned 500 total points
ID: 41870705
assuming Everything has passed Vmotion validity checker.

if it passes the Validity Checker, they can be vMotioned.

The VM memory session is sent across the vMotion network interface in the Host hosting the VM, it has nothing to do with vSwitch, Virtual Machine Portgroups.

why do you think they cannot be vMotioned ?

what don't you understand ?

why do you think they cannot be vMotioned ?

what do you think prevents them from being vMotioned ?

A VM can be associated to any Virtual Machine Portgroup, on ANY HOST. It does not prevent it being vMotioned, it's virtual. There is NO permanent connection to tie or hold it to a host.
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Author Comment

by:jskfan
ID: 41870721
Good job Andrew
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Author Closing Comment

by:jskfan
ID: 41870757
Excellent Explanation and Patience!!!
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LVL 117
ID: 41870843
No problem, always glad to help, and explain, now matter how long it takes!
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