I have a PFsense router, and a Linksys LGS308 gigabit switch connected to it. I'm using a cheap Linksys router to act as an access point. I want to try and simulate public IP addresses in a completely isolated LAN. Is this possible?
Also, I know this is a stupid question, but could someone PLEASE explain what on earth a subnet mask is? I'm a teen trying to learn all this stuff, and so I'm kind of having to teach myself and learn as I go, and subnet masks always confuse me. I am familiar with setting up things on the 192.168.x.x IP range, but I don't know how to use any other private IP ranges.
Yes, you can set whatever ip you want in your lan; Subnet mask is invention of past ages of ipv4 it was designed to conserve ip addresses, and also to easy management, configuration and identification of separate networks on one backbone... If you take a look at tcp/ip v4 packet the header with 255.255.255.254 is going to take most of allowed bit space for actual ip address so the bigger numbers in subnet will result in smaller pool of ip's allowed in this subent.
there are good cheat sheets here: http://www.aelius.com/njh/subnet_sheet.html
I recommend buying or downloading book - CCNA from cisco network fundamentals. The 192.168.x.x is one of the ips and is considered an internal ip but nothing is stoping you from using any ip that you want for internals. External are different story your outgoing network most likely will block you or you won't have access outside because there is no broadcast for the range you specified or maybe there are some filtering running...(which most likely are)
You can set you up address to whatever you want, but devices on the LAN side will only be able to communicate with devices on the wan side if they are on the same subnet as the wan interface. It won't work the same as the internet because everything on the internet is behind routers, this is what allows your network to communicate with other networks. With only a single router you can only communicate between 2 networks.
In other words; can you use your router to let two networks with different subnets communicate with each other? Yes. Can you use your router to let your LAN communicate with devices set up with random ip addresses? No, each side of your router (LAN and wan) have to have their own subnets and all the devices on those networks have to have the same subnet.
So a good example would be like I connected a small hub to two PC's they could only communicate but, if I was standing in a coffee shop connected to a WiFi all computers could connect to said device. Yes?
Not really. If you have a bunch of computers connected to a switch or a wireless network, if they are all on the same subnet then they can all talk to each other. If you add a bunch of computers which are using a different subnet to the same physical network then computers on each subnet will be able to communicate but a device from one subnet won't be able to talk to a device on another. For this you need a router.
So if you have a router with two interfaces, one is 10.1.1.1 and the seconds is 10.1.2.1 then devices connected to the 10.1.1.x network will be able to talk to devices on the 10.1.2.x network via the router. But if you added a device to the 10.1.2.x network with an ip address like 88.100.57.2 then devices on the 10.1.1.x network wouldn't be able to communicate with it. This is what I was saying to the OP, you can use public IP addresses on a local network (you shouldn't because it will mess with your internet connection) but you can't just use any IP for a device on the WAN side of your router, whatever devices you have there will need to be on the same subnet as the WAN interface.
The subnet mask is what identifies the network and host parts of an IP address. It can be pretty complicated and I don't fully understand it but a simple example is in a home network you might have an ip address like 192.168.1.1 with a subnet mask of 255.255.255.0, this means that the first 3 parts of the IP address are the subnet and the last part is the host address. It also means that there are 254 possible host addresses on that subnet.
Now if you have a device on the same network with an IP address of 192.168.2.1 with a subnet mask of 255.255.255.0 then the two device will be on different subnets and won't be able to communicate. One will be on the 192.168.1.x subnet while the other is on the 192.168.2.x subnet. But if the subnet mask is 255.255.0.0 then they are both on the same (192.168.x.x) subnet.
Really for home networking that's pretty much all you need to know, there's a bit more to it than that and again, I don't fully understand it, but that's the jist of it.
I'm always amazed by how intricate things can get. I remember taking programming courses and thinking damn looking the arrays you can put in arrays and put objects in those arrays. lol