VM Networking question

So guys,

I came across this config on a host and it puzzled me a bit. How could all the VMs attached to this vSwitch, still be getting network connectivity ?

My initial guess is  that once the vms were using a vmnic, then someone will have put all the uplinks into standby mode made they stayed connected?

The host is running ESXi 5.1
standbynics_edited.png
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piedthepiperAsked:
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asavenerCommented:
It works the same way it would it would with a physical switch.  A physical access-layer switch might have 22 ports for client devices, and only two uplink ports.  All of the devices on the switch can utilize the uplink ports, though.

Similarly, a vSwitch might have 255 virtual ports and four physical uplink ports.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
that is a possible theory, use esxtop and this will confirm, which VMs are using which uplink.

why someone would put all nics into standby is beyond me!
piedthepiperAuthor Commented:
Esxtop showed the vms using various up links out of the 4.

When you set them all as standby vcenter warns you that you have no active up links.

So my guess is that since the physical ports are active,  putting them in standby mode on the vswitch makes no difference on the vswitch as they are connected to the physical layer fine.

They are always up and as such the vms will use them

What a bizzare config
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piedthepiperAuthor Commented:
So it has been brought to me attention by ChrisWhal and other VMware admins/networking guys that if all the vmnics are set to standby, it will default to using the first one in the list as active as it will treat it like an active failure...as there are no active uplinks
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
We would much rather see a trunk of all four nics in use, and let the trunk decide and physical switch.

rather than just have 1 active nic in place, gives you more throughput and resilience at the same time.

especially if you have gone to the trouble of cabling up all four physical nics to physical ports, why not use them!

I don't think this sits in the Top 10 of VMware vSphere Best Practices!

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asavenerCommented:
D'oh!  Didn't even notice the NICs in standby....
piedthepiperAuthor Commented:
Absolutely it is nowhere near best practice, whoever set this up needs a talking to. I changed them all to active/active right away.

I wish I knew the thought process involved!
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