I have a remedial understanding of networking. I'm learning new stuff all the time but I'm still at a low level. If it were networking college I feel like I've just finished my first 200-level courses, but I also feel like there might have been a 100-level or two I might have missed. Therefore I do frequently butt up against the limits of my knowledge, particularly when my clients spring things on me that I hadn't anticipated (sometimes that's my bad).

Take, for instance, a church I do work for. They have a bizarre, patchwork network that I've basically had to Frankenstein into existence. There's some good equipment, with a Ubiquiti Edgerouter and Unifi APs all over the place providing WiFi.

The problem is that this network was designed for the staff, but now I've been asked to bring WiFi to the sanctuary and public areas so that the congregation can get online as well. I have no problem setting up the guest network and portals (the Unifi system makes this very easy), but I'm just going to run out of IP addresses. Between the office computers, IP cameras, wireless APs, printers, and staff smartphones, I'd say that there's perhaps 40-80 available addresses in the DHCP range, depending on the day. Now, this might not be much of a problem because I doubt there will be many people connecting to this, at least at first. But I'd rather not count on that.

So the question is: how do I make more addresses?

I'm limited in several ways. I'm limited in how the network is physically laid out because there's a conduit running between the newer building where the equipment rack is and the older building where all the offices are. It's possible I could separate the wireless users from the wired, but most of the office is using the wireless at the moment. The router has two interfaces (I've only configured and used one at the moment), so it's pretty capable.

I can't imagine that we'd need more than one additional subnet, but I don't know how this works. Is that even the right thing to do? Should I split out devices as best I can across two subnets, giving me around 500 addresses to play with? Would devices be able to communicate across those subnets? What about netmask? I'm not even sure what that is...

As you can see, I'm a little lost at this level.