Linux Hint published a tutorial about setting up a static IP address on Debian 11.
How to set up a static IP address on Debian 11
When you install a new operating system on your computer, the DHCP server assigns you a dynamic IP address. However, you may need to set up a static IP address on your machine in various situations, such as when you are hosting a web server, or any service requires an IP address rather than a domain name, or in a case where you are about to grant someone remote access to your system. This article explains how to set up static IP on Debian 11 Bullseye by two different methods.
