What do you mean by "make a complicated cluster of machines work together?" At the simplest level, you have a big switch in the middle of your servers that onl

What do you mean by "make a complicated cluster of machines work together?" At the simplest level, you have a big switch in the middle of your servers that only connects to other switches that then feed your servers. That's about all there is. You can pile on redundancies, bondings, vlans, software defined networks, and other things as needed, but with the minimum requirement of only "work together," those additional parts aren't required. (We're ignoring Internet connectivity here and just "making machines in one facility work together.") Everything is just tiny pieces. The tiny pieces get put together to grow networks larger. It can be complex, but it's not impossible to figure out. If you're working at a colo, ask a few people to draw you diagrams of how the facility's network is laid out. Then ask them to draw how a typical customer deploys their network within your facility. Ask, get confused, learn, ask more, then you'll have it all figured out pretty fast.