A dynamic IP address changes each time you restart your PC or router. If you made settings that rely on the IP address to stay the same (for example port forwarding), they would no longer work because the IP address has changed.
A static IP does not change. This is why it is often recommended to set up a static IP address in conjunction with other connectivity troubleshooting steps.
Setting up a local static IP is easy and can be done through Windows. Bear in mind that you only need to change your local IP. Your public IP can stay untouched.
Setting up a static IP
Start by opening the Control Panel. There, please navigate to Network > Network and Sharing Center.
Next, find Change Adapter Settings on the left and click on it.
Right-click on the active connection and select Status.
A new window will open. Click on Details.
Here, the details of your network connection will be displayed. Please write down the details or take a screenshot of this window because you will need the details later.
Close the window and right-click on your active connection again. This time, select Properties. From the options provided here, select Internet Protocol Version 4 (TCP/IPv4) and click on the button Properties.
Select Use the following IP address and enter the IP address you wrote down earlier. You do not need to enter an Alternate DNS server. In most cases, only the preferred DNS server will be used.
Next, select Validate settings on exit and click OK.
As a last step, please restart your computer. This should finalise your changes. You have now set up a static IP address.
If you want to reverse the settings at any point, simply choose Obtain an IP address automatically from this dialogue above and restart your computer.
For more information please check this Microsoft FAQ. Should you have trouble setting up a static IP address, we recommend that you contact Microsoft directly.