Have an ESXi instance version 6 or higher. VSphere is NOT required.
Install the requirements from the ESXi Terraform Provider
- If building on MacOS, don't forget to change the GOOS from linux to darwin!
  - GOOS=linux -> GOOS=darwin
Build and install the terraform-provider-esxi provider
Your ESXi must have at least two separate networks - one that is accessible from your current machine (VM Network) and a HostOnly network to allow the VMs to have internet access (HostOnly).
OVFTool must be installed and in your path.
- On MacOS, I solved this by creating a symbolic link to the ovftool included in VMWare Fusion: sudo ln -s "/Applications/VMware Fusion.app/Contents/Library/VMware OVF Tool/ovftool" "/usr/local/bin/ovftool"
On your ESXI, you must:
1. Enable SSH
2. Enable the "Guest IP Hack"
3. Open VNC ports on the firewall
- Instructions for those steps are here: https://nickcharlton.net/posts/using-packer-esxi-6.html
Install Ansible

Steps

(5 Minutes) Edit the variables in DetectionLab/ESXi/Packer/variables.json to match your ESXi configuration. The esxi_network_with_dhcp_and_internet variable refers to any ESXi network that will be able to provide DHCP and internet access to the VM while it's being built in Packer.
(45 Minutes) From the DetectionLab/ESXi/Packer directory, run:

PACKER_CACHE_DIR=../../Packer/packer_cache packer build -var-file variables.json windows_10_esxi.json
PACKER_CACHE_DIR=../../Packer/packer_cache packer build -var-file variables.json windows_2016_esxi.json
PACKER_CACHE_DIR=../../Packer/packer_cache packer build -var-file variables.json ubuntu1804_esxi.json

These commands can be run in parallel from three separate terminal sessions.

(1 Minute) Once the Packer builds finish, verify that you now see Windows10, WindowsServer2016, and Ubuntu1804 in your ESXi console
(5 Minutes) Edit the variables in ESXi/variables.tf to match your local ESXi configuration or create a terraform.tfvars file (RECOMMENDED) to override them.
(25 Minutes) From DetectionLab/ESXi, run terraform init && terraform apply
Once Terraform has finished bringing the hosts online, change your directory to DetectionLab/ESXi/Ansible
(1 Minute) Edit DetectionLab/ESXi/Ansible/inventory.yml and replace the IP Addresses with the respective IP Addresses of your ESXi VMs. These IP addresses much be reachable from your host machine!
(3 Minute)s Edit DetectionLab/ESXi/resources/01-netcfg.yaml. These are the IP addresses that will be applied to the logger network interfaces. These should be be able to be found in your ESXi console or from the Terraform outputs.
(3 Minute) Before running any Ansible playbooks, I highly recommend taking snapshots of all your VMs! If anything goes wrong with provisioning, you can simply restore the snapshot and easily debug the issue.
Change your directory to DetectionLab/ESXi/Ansible
(30 Minutes) Run ansible-playbook -vvv detectionlab.yml
If all goes well, you should see the following and your lab is complete!

If you run into any issues along the way, please open an issue on Github and I'll do my best to find a solution.

Future work required

It probably makes sense to abstract all of the logic in bootstrap.sh into individual Ansible tasks
There's a lot of areas to make reliability improvements
I'm guessing there's a way to parallelize some of this execution: https://medium.com/developer-space/parallel-playbook-execution-in-ansible-30799ccda4e0

If an Ansible playbook fails, you can pick up where it left off with ansible-playbook -vvv detectionlab.yml --start-at-task="taskname"

As usual, this work is based off the heavy lifting that others have done. My primary sources for this work were:

Thank you to all of the sponsors who made this possible!