For real life, a campus network is a big/major project.
From scratch, you start with number of hosts you need to support, how they need to be supported, and, of course, where the hosts will be. Budgets for building a network, generally, also come in to play early in the process.
Once you have the network requirements, you start working on designs, and contacting vendors (not just for hardware like routers/switches/etc., interior/exterior cabling vendors/departments, service providers [ISP/WAN/MetroE]). You're also provide a project plan for everything you're responsible for.
In the real world, designing the network, at least at a high level, is often the "easy" part. Designing down to all the little details, and working out schedules (and keeping them), is what's hard. Something like a new building, or new network installation, of a large size, can be, just for the network components, a multi-month project.
Although such projects are generally multi-month, they are not full time, so in the real world, you have many other projects going on concurrently.
If you're lucky, you'll never need to build out something like a campus, from scratch, without either/both having experience doing such before, or working from real world examples your company has done before.
Personally, my biggest project, that I was fully responsible for, was building a network, from scratch, for a newly constructed 2,000 person multi-floor call center. Again, in the real world, many from scratch issues were already somewhat addressed. For example, we already had standards for network equipment, and because of those, many budget issues were also covered. Yet, some things I had to work out from scratch. For example, being a call center, "failure was not an option". So even though my design had two MetroE connections, I had to arrange for a link be run down the street to a near by commercial hosting center, so I could utilize their links as a VPN backup path, via their Internet connections. (I had to arrange to rent a cabinet, but without anything in it, other than my link [from street] to their internal connections to the Internet]. It was also my job to negotiate cabinet rental and bandwidth charges.)
When the call center become active, part of my responsibilities was to arrange a "live" test of failing both private links to demonstrate VPN backup would support the call center. (BTW, test was passed.)
So, to recap, designing and implementing a campus network is major/big project, which, in the real world, is much more involved than just the actual design of the network itself.
