New in Hyper-V Windows Server 2008 R2 Part 1 – Dedicated Networks

I thought I’d start a series of posts highlighting some of the smaller changes in Hyper-V in Windows Server 2008 R2. There’ll be plenty of people covering the larger features such as Live Migration, so I figured someone needs to cover the other fun stuff!

Many of the improvements are not visible from an end use perspective – changes such as code cleanup, bug fixes, optimizations for performance and scalability. But many are visible, and this post covers one such change.

I did a post back in June last year covering how networking works in Hyper-V and followed it up with a description of the uses for the different types of networks. That second post left you somewhat dangling, as the “best practice” type of network for virtual machine connectivity is what I called (as there wasn’t an official name back then), a “dedicated” network. This type of network is depicted below. But, there was no way to create such a network in Hyper-V “v1” user interface without scripting.

This type of network has a virtual network switch bound to a physical NIC, but no virtual NIC present in the Parent partition (aka Root partition or “Management Operating System”). In other words, it can only be used by virtual machines, not the parent partition.

Robert did come up with a script to create a dedicated network, but the “v2” UI (present in full installations of Windows Server 2008 R2 and RSAT in Windows 7 client) has a new checkbox to do just this, marked “Allow management operating system to share this network adapter”.

The good news is that using the “v2” UI, you can target both a “v1” and a “v2” server running the Hyper-V role (or Microsoft Hyper-V Server) and this checkbox and functionality is available.

Hence, if you have not so far scripted a way to create a “dedicated” network, or have chosen to simply disable the virtual NIC in the parent partition or even unbound all protocols from that virtual NIC, now’s the time to revisit your configuration.

One thing I should mention is the default when creating a new external virtual network – in particular the (not recommended) case of a single physical NIC machine being remotely managed. The default is that the checkbox is not checked. Hence, you should be sure that if you do not allow the management operating system to share the network adapter, there is an alternate NIC available for management. Obviously in the single physical NIC machine scenario, not checking this box would probably mean a trip to the server room… Hopefully the warning is clear enough!

Cheers,
John.

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