In which mode can you issue the command to configure a device's interfaces?

Configuring a device's interfaces is primarily done in global configuration mode. This is the mode where you can make changes that affect the entire device, including configuring interfaces, routing protocols, and various other settings.

When you enter global configuration mode from privileged EXEC mode, you enable the router to accept configuration commands. Here, you can access the interface configuration mode to specifically configure individual interfaces of the device. This capability distinguishes global configuration mode from the others, which have more limited functionality.

In user EXEC mode, you can run basic commands and view device status, but you cannot make any configuration changes. Privileged EXEC mode allows users to access more detailed information and execute a broader range of commands, but it is still not where configuration commands are entered. Router configuration mode is often used to denote the mode that is specific to configuring router settings, but it is not the term used universally for interface configuration in all device contexts, as it most often refers to router-specific command input, lacking the broader application of global configuration mode.

Therefore, the correct and most specific answer regarding the environment in which interface configurations are made is global configuration mode.