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Oct 06 2009
VMware Virtual NIC Choice and SYSPREPing Templates Print E-mail
Written by Paul Winkeler   
Tuesday, 06 October 2009
Under ESX 3.5 an enhanced NIC choice called vmxnet became available but only to 64-bit VMs. The idea behind this new virtual device is that by publishing itself as TCP/IP offload capable, the Windows OS will not bother to encapsulate data into a TCP/IP packet before handing it to the ethernet driver, instead leaving that task to the (virtual) hardware. As a result, the vmxnet device no longer has to parse and strip the TCP/IP packet information so it can hand the payload off to the *real* physical NIC and everybody wins.

This improvement was big enough that numerous VMs have been changed to 64-bit even if the guest Windows OS was still 32-bit; all just to gain access to that more efficient NIC. But guess what? No good deed goes unpunished and indeed neither does this one. When one of my customers came to me a few weeks ago with a scenario that prevented her from SYSPREPing a VM she tried to create from a template even after installing every SYSPREP CAB's contents into all possible folders, we, as well as VMware support, were stumped. Finally we discovered that the reason the option to customize the template deployment was grayed out was because of the mismatch between a 64-bit VM and a 32-bit guest OS! All we had to do was convert the template to a 32-bit VM and everything worked as advertised.

My biggest gripe here is that the VMware GUI gave absolutely no feedback to this effect. None. Zero, Zip, Zilch. Ah well, live and learn.

Last Updated ( Tuesday, 06 October 2009 )
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