Internet is full of useful stuff and also a bunch of people talking out of their … dunno, you could look at “eli the computer guy” videos that explain ethernet switch/hub and subnetting as a start, and maybe find some free youtube CCNA training videos if you have more time.
If you don’t, here’s a crash course.
You don’t need to use DHCP, you can always type addresses in manually. DHCP gives you 3 basic things:
- tells your computer what your computer ip and subnet mask should be - from which your computer will be able to tell what things are on the same local network.
- tells your computer of a gateway ip address, which identifies a target where your computer will send everything else not on the same local network. (gateway ip has to be on the local network).
- DNS is the service used to translate hostname<->ip address, obviously generally useful for browsing and other stuff.
You can configure all of these by hand for each of your interfaces in network properties and thus not use DHCP if you don’t want to.
Specifically, way this first thing works is …
…when you look at the ip address and subnet mask, all bits in your ip address, that have 1 in the subnet mask, are all the same on all hosts in your network. Additionally, in the subnet mask, all left bits are 1s, all right bits are 0s, because of that ip/subnet mask is frequently written down as ip/number_of_ones. For example, configuring the interface with ip/netmask of 192.168.1.101/25 will tell your computer that 192.168.1.1-192.168.1.127 are directly connected to it, and it needn’t bother the gateway (you can find ip address calculators online that illustrate this, or you can do a bit of pen and paper math).
Way second thing works is via routing tables, most hosts will only have one way to reach the internet, and some stuff on the same local switch (or a router that just happens to have a switch built-in where hosts on the same subnet are connected, and a wifi access point that’s basically like a wireless ethernet switch).
Because there’s only local lan/internet these routing tables are very simple.
Typically they’d look like:
192.168.1.0/25 on ethernet_interface_1 (locally connected)
0.0.0.0/0 via 192.168.1.1 (default gateway route)
When your computer needs to send a packet out, it looks up in the routing table, and picks a route that matches the destination ip address (the most specific one).
You might also find 127.0.0.0/8 in your routing table which is just always there traditionally as a “loopback” route if a host wants to talk to itself via IP… (turns out it’s useful for some things).
VPN interfaces, if you’re referring to typical providers, aren’t configured through DHCP. But there will be interfaces and addresses and routes and in your routing table there might be multiple ways of reaching the internet over multiple interfaces. Most VPN providers give their clients skinned OpenVPN software (skinned with the VPN company logo and scripts and some on/off toggle buttons maybe with animations, maybe an auto updater) and OpenVPN will use the existing network to establish a network connection to their service, and will then run a script your VPN provider configured to setup routes and IPs on your windows host. Naturally you don’t have to use your VPN providers apps and can use VPN with your own config instead - they even provide documentation on how to do this, it’s often the only thing they support for non windows hosts.
Maybe you should go and look at some of that other basic networking stuff and let that sink in first (or CCNA if you’re really interested) and come back if you have more questions? There’s a gazillion ways these things can be configured, any particular individual guide might be glossing over a bunch of detail that’ll likely make it not work for you - having some networking knowledge might help you follow along and troubleshoot particulars of your setup if/when you get stuck.