That’s a really great question: Should you use Class A, Class B, or even Class C private addressing when setting up your network? Let’s take Acme Corporation in San Francisco as an example. This company is moving into a new building and needs a whole new network (what a treat this is!). They have 14 departments, with about 70 users in each. You could probably squeeze one or two Class C addresses to use, or maybe you could use a Class B, or even a Class A, just for fun.
The rule of thumb in the consulting world is, when you’re setting up a corporate network— regardless of how small it is—you should use a Class A network address because it gives you the most flexibility and growth options. For example, if you used the 10.0.0.0 network address with a /24 mask, then you’d have 65,536 networks, each with 254 hosts. Lots of room for growth with that network!
But if you’re setting up a home network, you’d opt for a Class C address because it is the easiest for people to understand and configure. Using the default Class C mask gives you one network with 254 hosts—plenty for a home network.
With the Acme Corporation, a nice 10.1.x.0 with a /24 mask (the x is the subnet for each department) makes this easy to design, install, and troubleshoot.