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VMware:  Virtual switches and multiple NICs

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Last Modified: 2017-04-23
Hi,

I have difficulty understanding NICs and Switches in VMware.
At client's sites I often see more than one NIC connected to a single virtual switch.  These are then connected to one single physical switch.

In the physical world, I would at worst expect this to give you a signal loop and at best no gain, as spanning tree would prevent worse from happening.  That is unless you actually configure your switches to use multiple links as a trunk.

I am not aware that this can be done with virtual switches.  So:  What is the use of connecting more than one NIC to the same (let's assume) unmanaged switch?

Thanks,
Ralph
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Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Commented:
I have difficulty understanding NICs and Switches in VMware.
At client's sites I often see more than one NIC connected to a single virtual switch.  These are then connected to one single physical switch.

In the physical world, I would at worst expect this to give you a signal loop and at best no gain, as spanning tree would prevent worse from happening.  That is unless you actually configure your switches to use multiple links as a trunk.

Possibly, it depends on the teaming policy selected on the Host.

Also it's worth reminding you, that the teaming policy on the host, controls the outbound traffic from the host, and the configuration of the physical switch ports, controls the inbound traffic to the host.

I am not aware that this can be done with virtual switches.  So:  What is the use of connecting more than one NIC to the same (let's assume) unmanaged switch?

The teaming policy configured on the host needs to match the physical switch.
Ralph ScharpingDigital Therapist

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Commented:
Thanks.  Now I'm struggling with the translation, as vSphere Client seems to always use the language of the OS.
This translation seems to be a bit ... off.

I get load balanching and traffic shaping options.  But where do I configure teaming?

I'm on the host at Configuration -> Network and there in the property of the virtual switch.
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Commented:
Teaming Policy on the vSwitch Properties.

Teaming = load balance and resilience!
Ralph ScharpingDigital Therapist

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Commented:
Is trunking an option?
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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There is no policy called Trunk - have you looked at all the teaming policies, did you see one called trunk ?

 because you must match the Teaming Policy you have configured on your Host with the Configuration of the Switch.

Unmanaged Switch, has no trunking configuration!

Also it's worth reminding you, that the teaming policy on the host, controls the outbound traffic from the host, and the configuration of the physical switch ports, controls the inbound traffic to the host.
Ralph ScharpingDigital Therapist

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Commented:
No, I did not see one - that's why I asked.  
I'm sorry to annoy you.

Assuming the physical switch supports trunking, is there a way to configure this in VMware?
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Ralph ScharpingDigital Therapist

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Commented:
Thanks, Andrew.
Andrew Hancock (VMware vExpert PRO / EE Fellow)VMware and Virtualization Consultant
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Commented:
no problems, Networking is the number 1 issue, we see day to day on installations we visit, because VMware Admins are not Networking Admins!
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