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I'm assuming ESXi will act very similarly to VMware Workstation or other products, so answers based on knowledge of those programs might also help.

I want to plug in 30 USB Wireless or Ethernet adapters into my server, and let each VM access one and only one of these devices.

Unfortunately, I don't have the hardware to just try it out as the purchase of hubs and adapters hinges on the result of this question.

The answer could be a resounding "yes, easy!" and that would be great. I couldn't find any answers to this question with google, and it's possible that this is because it's so easy to do.

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up vote 3 down vote accepted

I have strong doubts about whether this would work. ESXi does support USB hardware passthrough, but not for every type of USB device.

Our system coped fine with USB memory sticks and a USB lead to a UPS for monitoring it, but ESXi would not 'see' the card/fob reader for our building security system so we could not pass it to a VM.

Probably best to contact VMWare themselves.

Edit: Read these knowledge base articles:

  • USB support for ESX/ESXi 4.1

  • Supported USB device models for passthrough from an ESX or ESXi host to a virtual machine

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Hmm, thanks for the info, I'll look into that tomorrow. – 31eee384 Jun 21 '11 at 5:37
According to your first link, "The USB arbitrator can monitor a maximum of 15 USB controllers. [Additional controllers] are not available to the virtual machine." If I understand what a USB arbitrator is, that completely obliterates the possibility of having 30+ USB network adapters used directly by the virtual machines. Hmm. Now I'm thinking that if each network adapter was recognized by the host, VMware could potentially give each connection to a VM. From this document: it seems that maybe it would work, depending on adapters. – 31eee384 Jun 21 '11 at 15:40
(I was going to add that I'm currently looking into this, and will post another question if I can't find the information I'm looking for--but I ran out of characters. Thanks for the help, Linker3000!) – 31eee384 Jun 21 '11 at 15:46
Sorry for all the comments, but I'm pretty sure I messed up... I didn't understand that there is a difference between USB controllers and USB devices. In that same document, it says that 20 USB devices can be added to a single VM, which contradicts my earlier thought that only 15 would be allowed and re-expands my search. Sorry again for the commentspam, and thanks for the links. – 31eee384 Jun 21 '11 at 16:09
Hope you get a definitive answer - I think it's still likely that this can only come from VMWare themselves. I still worry that you won't find a supported adapter. – Linker3000 Jun 21 '11 at 16:55

USB RJ45 adapters work just fine in my testing. I have even used USB bluetooth adapter to passthrough a keyboard+mouse and USB serial to remotely connect serial devices.

When you go into the settings for a VM (in esxi), you have the option of passthrough a host USB device permanently into a VM. I see no reason why this will not work for your setup.

Some of your devices may work (as you mentioned) directly on the ESXi host, then just use a vswitch to give the VM exclusive access to that adapter. Others that do not work (wireless ones), do the passthrough method.

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