Sorry for using such a vague title, I can’t really think of a good way to word it but, I know that using a VPN will mask your IP Address but I’m wondering does it modify your actual router or is it just modifying the device you have the VPN program on. [For example if I use Tablet A and use a VPN to change the IP Adress will it just be Tablet A that changes and Tablet B, C and D remain with the original ID Adress OR will all of the devices on the network change their IP Address?]
It doesn’t mask your IP address. It changes the route your device takes to the Internet.
It routes all of the internet traffic on the device using the vpn to one server via an encrypted connection before then moving on to the rest of the internet.
Which device you apply VPN on, it will be affected by the VPN. If you use it on a smart phone, it will be covered, and not the others on the same LAN. If you apply it on the router, all devices covered by the router can be covered. Depending on the capability/setting of the router, you can choose which device under the router is covered by VPN.
When you use a VPN, it only affects the device on which the VPN app or software is running. For example, if you have the VPN running on Tablet A, only that tablet’s IP address will appear as changed. Tablets B, C, and D will still use the original IP address assigned by your router. The VPN doesn’t modify the router or other devices on the network unless the VPN is set up directly on the router itself.