Windows Insider

Can't Use DHCP? Try VMM 2012 IP Pools

System Center 2012 SP1's Virtual Machine Manager IP pools offer the same zero-effort IP addressing experience that desktop administrators have enjoyed for years.

• By Greg Shields
• 05/08/2013

System Center 2012 SP1 Virtual Machine Manager (VMM) is big. It's arguably one of Microsoft's most-visionary releases yet. Buried inside you'll find an almost-overwhelming array of new features and capabilities worth investigating. Integrate VMM with the rest of System Center 2012 and its automation potential only gets that much more impressive.

But in and among all of the VMM big-name features, sometimes it's the little things that matter most. One such tidbit is an easy-to-miss but powerful feature called IP Pools. These you'll find inside the fabric in VMM as resources to configure on Logical Networks.

IP Pools are best described by what they aren't: They aren't DHCP. They might look like DHCP and they might behave like DHCP, but VMM IP Pools are an altogether different animal.

These nifty little VMM constructs enable a DHCP-like experience for Windows Server VMs. They introduce all the best parts of DHCP to server address provisioning, but without being DHCP itself. What results is the same zero-effort IP addressing experience that desktop administrators have enjoyed for years.

Servers Aren't Desktops
Now, for Windows Server. For such a simple thing, I'm amazed no one has thought of this before.

Most IT pros recognize that IP addressing works differently on servers than on desktops. With desktops, the specific IP address given to a machine is generally less important than that machine merely possessing one. With desktops, you tend to care more about having an IP address than having a specific IP address. In those occasional situations where you must connect to a desktop, services like dynamic DNS registration -- and, in the old days, Windows Internet Name Service, or WINS -- facilitate the necessary IP-to-hostname resolution.

IP addressing for Windows servers has much different requirements. By definition, servers provide services. Servers also tend to work with other servers and datacenter hardware in accomplishing that goal. As a result, server addresses are necessarily static. Once set, they rarely -- if ever -- change.

Unchanging IP addresses are also important for interconnecting the rest of a datacenter's hardware and apps.

IP Pools
It's here where the beauty of VMM IP Pools becomes evident. An IP Pool is exactly what it might seem: a series of addresses you assign VMs as they're provisioned. It's how they're distributed that's different. Rather than being delivered via a DHCP client, IP Pool addresses are instead injected directly into each VM as it's created. Other addressing info such as DNS servers, WINS servers and gateways are also statically assigned.

What results is a kind of hybrid address management solution that's at the same time dynamic and static. Addresses get distributed from IP Pools similar to how DHCP operates, but look inside any VM Network Connections control panel and you'll find an old-fashioned statically assigned address. Unlike DHCP, however, static addressaren't time-sensitive. Static addresses aren't returned back to the IP Pool until the VM is deleted or the address is forcibly removed, the latter of which requires the help of Windows PowerShell.

With everything that's great about the implementation of VMM 2012 IP Pools, I see only one small omission. Using VMM alone, there isn't an easy way to track which address has been assigned where. One can obviously check DNS for their registration, but no support exists directly in the VMM interface for visualizing address distribution. That task today is left to a new Windows Server 2012 feature: IP Address Management, or IPAM. While the details of IPAM are the topic for another day, this feature offers automated host discovery, address utilization trending and a variety of other tools to manage a datacenter's static (and dynamic) address spaces.

All in all, IP Pools are a great way to automate what used to be a chore for server-provisioning IT pros. I remember a time not long ago when merely getting an IP address was an action that could take hours. Now for all of us, static seemingly is the new dynamic. Or, maybe dynamic is the new static. In either case, take a look at VMM 2012 IP Pools .