I would consider adding an indicator to the racks that shows how many servers are currently filled, as when you have lots, it may not be obvious which ones you filled and which are empty, even moreso when you upgrade them to higher capacity and already had previous ones.
Also, the option to sell servers which havent reached their lifespan to upgrade them to better one could also be nice.
Overall, it's a really cool concept, I like idle games, and there aren't many of them focused around networking/infrastructure, with a bit more polish it could turn into a really nice idle game. Great job!