Hyper-V : The Differences between a the “Network adapter “and the “Legacy Network adapter”
In Hyper-V there are TWO kinds of network adapters inside the virtual machines, first there is the "Network Adapter" and then there are the "Legacy Network Adapter". The difference between those are very simple. The Legacy Network Adapter is needed when you need PXE boot OR your OS needs access to the network before you can install "Integrated Components". That happens when you try to run "Some new package solutions from Microsoft" on Hyper-V. The "Network Adapter" requires that you install "Integrated Components" (yes the contain the synthetic driver that is required for the Network Adapter" to work. So if you want to be 100% sure that the network is going to be there during the installation phase, use the "Legacy Network Adapter".
When the OS is installed, add the integrated components. If you install "The new server solution" you will have to wait until the setup is complete or you can use the "Shift-F10" function. Pressing Shift-F10 when the OS is installed but you don't have explorer up yet, brings up a command prompt, then use the Hyper-V tools to insert the Integrated Components ISO image and install the IC from the CMD prompt (32 bit is in the x86 folder and the 64bits are in the amd64 folder), and then restart. The simplest way is to use the "Legacy Network Adapter" all the way trough the install phase, then add the Integrated Components, shut down, edit the settings and remove the "Legacy Network Adapter" and replace that with an "Network Adapter", you also may want to be sure that the boot order is correct since that could have been changed.
So to simply this:
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Create the Virtual Machine in Hyper-V, select to "install the operating system from the network". Dont start the machine
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Edit the machine so that you have 2 or four CPUs (This only works with some OS, among thooese are W2K8 64 bit)
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Change the boot order so that this fits your purpose (Boot on ISO is preffered)
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Start the machine, run trough the installation, finnish and install the "Integrated Components"
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Shut down the virtual machine, edit the settings and replace the "Legacy Network Adapter" by removing it and then you add a "Network Adapter"
One question you might ask is "why?", simple answer, The Legacy Network Adaapter is a bit slower as it runs in the workprocess in ring 3 in the parent partition, the "Network Adapter" uses the new highspeed vmbus instead.
note: "The new server solutions" are not supported on Hyper-V (This could however be changed in the future)
note 2: One thing to keep in mind here is that if you select to install from network (when crating the machine), Hyper-V is going to select a "Legacy Network Adapter", otherwise it picks the "Network Adapter"
Mikael Nystrom
MCP, MCDST, MCT, MVP Windows Server - Setup/Deployment
