Cisco Certified Network Associate (CCNA) Practice Exam 2026 – The Comprehensive All-in-One Guide to Exam Success!

To configure an IP address on a serial interface, the command that initiates the configuration mode is "configure terminal". This command places you into global configuration mode, where you can make changes to the device's configuration, including interfaces.

Once in the global configuration mode, you would then access the specific interface (for example, the serial interface) using the appropriate command, such as "interface serial0/0" (or similar, depending on the specific interface designation). From there, you can assign an IP address with the command "ip address [address] [subnet mask]".

This command is foundational for network configuration because it opens the path to modify various settings on a Cisco device, which is essential for any further interface-specific configurations. Thus, it is the correct choice for starting the process of configuring an IP address on a serial interface.