Automatic Virtual Machine Activation (AVMA) is not a new feature but bears repeating as I run across many who forget that it exists or how it works. Simple but powerful, AVMA is a Server 2012 R2 Hyper-V feature that comes at the Datacenter license level and allows an unlimited quantity of seamlessly activated Server VMs on the same host. Very important to distinguish that this does not apply to Windows desktop OSes! Those must be purchased and activated separately using traditional methods. A popular workaround here, useful for other reasons as well, is to deploy Server VMs for use as desktops with the Desktop Experience feature.

Round numbers based on list pricing, if you have 10 or more server VMs to run on a single host, a Datacenter license probably makes good fiscal sense. Considering that a Standard license entitles you to 2 server VMs, below that number it will likely be cheaper to just buy Standard licenses, however you won’t get the AVMA feature.

Implementing AVMA is easy and best done against your template to be cloned either manually or by SCVMM. Once your Hyper-V host is activated, open an elevated command prompt on the Server VM you intend to use as your template and run:

slmgr /ipk <AVMA key>

Insert one of the keys below depending on the type of Server VM and features you intend to deploy. These are universal AVMA keys for use in any environment.

Server Edition	AVMA key
Datacenter	Y4TGP-NPTV9-HTC2H-7MGQ3-DV4TW
Standard	DBGBW-NPF86-BJVTX-K3WKJ-MTB6V
Essentials	K2XGM-NMBT3-2R6Q8-WF2FK-P36R2

Resources:

Server 2012 R2 AVMA