OSSIM (Open Source Security Information Management) is a free solution that allows you to take better control of your network and hopefully prevent intrusions as well as detect and test against them. OSSIM gives you black hat functions for learning and testing purposes. The setup is incredibly simple, download the .iso and spin up where you like: https://www.alienvault.com/products/ossim. I ended up configuring a resource account to use in order to deploy OSSIM agents on my network. It's often best to import your hosts using a .csv file unless you want to add manually you'll want Hostname/IP/OS. This information can be pulled easily by utilizing get-ADcomputer via PowerShell. https://blogs.technet.microsoft.com/askds/2010/02/04/inventorying-computers-with-ad-powershell/ After you've imported your list you can choose to deploy the OSSIM agent straight from the setup wizard.
Once you've imported your hosts into OSSIM you need to specify what functions each server serves (DNS, DHCP, WEB, DB, etc.) this helps provide extensive and organized reports. You can also divide the assets by groups. I believe this is most effective when done by environment name and/or client. Clients often want compliance & security reports when providing SaaS.
If you're looking for compliance or reporting on your servers, I highly recommend this product. The rest is very simple and all functions are available via the web GUI. Check it out sometime! For free you can't beat it. Heck, it even beats out some paid competitors.