Build
A redundant DNS - Pi-Stack
Without DNS nothing works. On any corporate network you will find several DNS server, several NTP servers and a lot of Firewalls. – Shouldn't the lab also have multiples of the core services, just in case.
Networking
Networking is one of the hardest things in building working clusters of servers. It's also the most vulnerable parts of your hole setup. The WAN interface is under attack 24/7 - by professionals and military.
