|I have all this gear. Not.|
Then I came across an interesting little piece of software called Packet Tracer from Cisco. It amounts to a software simulation of all kinds of Cisco and generic networking gear.
|Same thing in Packet Tracer.|
The routers and switches have command-line interfaces and GUIs like the real gear. You can add IP addresses, netmasks and dynamic and static routes. Then add and configure some PCs and ping the opposite node to see if it all works. If you get it wrong the error messages are what you'd get in real life.
|CLI from a Cisco 1941 router.|
I've only played around with it for a few hours but so far it seems to work as advertised. And once you register for an account (free) you can download it for Windows or Linux, also for free.
Now I can crash enterprise networks and not get fired. Yay!