Building a Lab in Hyper-V with PowerShell, Part 1

Setting the MAC Address Range on a Hyper-V Host


Today I want to start a new series of posts on building a lab environment in Hyper-V, primarily using Windows PowerShell to do initial configuration. For some things, you'll need to use a non-PowerShell tool, such as SysPrep or even the Hyper-V Manager. But the vast majority of the process is going to be pure PowerShell. And, to be clear, this is exactly how I build labs. I do very little checkpointing (snapshotting), preferring to rebuild to a known point rather than assuming I've gotten the right snapshot. And with a good set of scripts, and properly configured .VHDXs for source files, that's not really hard.


To understand how I build the base environment, you'll need to understand some assumptions I make and why. The first thing I do is configure the MAC address range for the lab host in Hyper-V. This avoids potential conflicts with other machines that might be on the network, especially since I'm going to be manually configuring all the MAC addresses for the VMs I create to allow me to easily configure DHCP reservations for all VMs. All of which makes keeping track of things much, much easier.


When Hyper-V hands out MAC addresses dynamically, it creates a range that begins "00-15-5D". This is the Microsoft IEEE Organizationally Unique Identifier, and is used for all Hyper-V generated MAC addresses unless we do something to change that prefix. Don't, you risk conflicting with some other company's range of addresses.


The next two pairs in the MAC address range are based on the current IPv4 network address(es) on the host itself if we don't manually configure them.  For lab environments, I usually set the first pair (fourth pair overall) to C8, C9, or CA, depending on which host machine I'm on, and the next pair to a number related to the IPv4 network that will be the primary network for core VMs in the lab. So, when I use a simple 192.168.10/24 network, I set that 5th pair to 0A. This gives me a MAC address range from 00-15-5D-C8-0A-00 to 00-15-5D-C8-0A-FF unless I need a larger range. If I'm going to have multiple networks and multiple NICs on lab VMs, I'll set a larger MAC address range.


To set the MAC address range on a Hyper-V server, you could use the GUI, but where's the fun in that. Instead, use the Set-VMHost cmdlet, thus:

Set-VMHost -MacAddressMinimum 00155DC80A00 `
           -MacAddressMaximum 00155DC80AFF `

Now, I set my new VM script to default to this range as well, and I edit the CSV file that creates DHCP addresses to the same range. But more on setting fixed or reserved IP addresses and configuring DHCP later in the series.  Next up, we'll start building the parts of New-myVM.ps1.