If you are studying for the VCAP5-DCA you definitely need a lab. If you are studying for the VCP probably need a lab unless you are in vCenter all day at work. Nested virtualization runs one hypervisor upon another; so a nested ESXi lab runs the ESXi hypervisor on another hypervisor like VMware Workstation. So why build a nested lab instead of a physical lab?
Flexibility - A nested lab on workstation is going to provide more flexibility than a physical lab. I have both, and I love having the ability to create another ESXi host in minutes by cloning it from a template. I can also turn off my 5.0 lab I am using to study for the VCAP5-DCA and turn on my 5.5 lab and show a coworker a new feature.
Cost - The cost of a nested lab can be cheaper than the cost of a physical lab, especially if you have box that you can simply upgrade the RAM in. When building a computer to run a nested lab the cost could be similar or more than buying used servers from eBay, but the power consumption should be much less. Building a low power solution like Intel NUC or MAC Mini's combined with a Synology will cost more than building a nested lab.
Portability - A small nested lab can run on a laptop allowing you to study on the road.
What do I need to build a nested lab?
How do I build a nested lab?
1. Prepare the computer
2. Create VM templates for linked cloning
This procedure should work on 5.0 or 5.5, and there is a detailed guide to preparing ESXi templates by Josep Piscaer here:
You normally need more than one NIC in ESXi, I like to use six. Instead of putting all six in the template I start out with one then add them one at a time so I can keep them straight. If it starts up with six NICs sometimes it can be tough to determine which is which without upstream CDP.
Set sysprep.exe to shutdown the machine upon completion. Find a more detailed guide here:
Convert VMs to Templates : Once the ESXi and 2012 Windows Server virtual machines are customized, generalized, and powered off they can be converted to templates. The first step is to edit the settings of the VM, go to the options tab, advanced, and check the template option.
3. Build the "Shared Infrastructure" VMs
Openfiler : ESXi labs need some type of storage. I like to have both NFS and iSCSI available. Openfiler is easy to install, easy to configure, and can provide both types of storage. The basic steps are to install openfiler, give it a static IP, present one disk via NFS, and present a second disk via iSCSI. While openfiler is easy to use the interface isn't intuitive for a non-storage person. Luckily the guys at labguides.com have a great openfiler lab that walks you through installation, NFS, and iSCSI.
I give openfiler a small disk for the OS, then a large virtual disk for iSCSI and a large virtual disk for NFS. There isn't a reason to present multiple disk for software raid.
AD Domain Controller : This component is really optional, but I like to have a DC available to provide AD integration for authentication in my labs. To bring up our AD DC we now get to use our Windows Server 2012 template we just created. Right click on the template, manage, and clone.
Edit the VM name to something more descriptive than "Clone of 2012 Template" and click finish to complete the clone.
When the clone is created I like to move my "Shared Infrastructure" VMs into their own folder and keep them separate from lab scenarios. Once I move the VM it's ready to power up, run through the small sysprep customization, and promote to a domain controller. It's been well over a decade since I was responsible for domain controllers, if you need further advice on this step you are barking up the wrong tree. I still keep trying to run dcpromo.exe.
Microsoft has a guide available here :
At this point I have two folders, Templates and Shared Infrastructure. These folder contain the building blocks I will use to construct lab scenarios.
4. Build a Lab Scenario
I use the browser and vSphere client from the host Windows 7 machine to manage vCenter. The host machine running Workstation will have access to all of the networks created.
There are even guides to get Hyper-V running on Workstation, or entire cloud frameworks like Openstack. The only limit is the amount of RAM on the box.