If you want administrators to see a message every time they log in to a Cisco router, which global configuration command should you use to configure this Message of the Day banner?

Introduction / Context:
This question focuses on basic Cisco IOS configuration related to login banners. Organizations often display legal notices, security warnings, or informational messages when users connect to network devices. The Message of the Day banner is a standard way to present such messages to administrators and users at login time.

Given Data / Assumptions:
- The device is a Cisco router (or similar IOS based device).
- We want a message displayed to anyone who connects to the router, usually before the login prompt appears.
- The question asks for the correct command format for configuring this banner in global configuration mode.

Concept / Approach:
On Cisco IOS, the banner motd command is used in global configuration mode to define the Message of the Day banner. After the command, you specify a delimiter character and then type the text of the banner, ending with the same delimiter. This banner is displayed on console, Telnet, and sometimes SSH connections before login. Other keywords such as banner login and banner exec are available for different banner types, but banner motd is the classic answer for a general login message.

Step-by-Step Solution:
Step 1: Enter global configuration mode on the router, typically with configure terminal.Step 2: Use the command banner motd followed by a delimiter (for example, #) and then type the desired message.Step 3: End the banner by typing the delimiter character again on a new line.Step 4: Verify that the banner appears when you disconnect and reconnect to the router.Step 5: Recognize that the syntax message banner motd or message motd does not match IOS command structure, whereas banner motd does.

Verification / Alternative check:
Documentation and lab exercises commonly show examples such as banner motd #Unauthorized access is prohibited#. Logging in to the router after applying this configuration displays the message between the delimiters before you see the Username or Password prompt. This practical behavior confirms that banner motd is the correct command to use for a general login message.

Why Other Options Are Wrong:
Commands like message banner motd and message motd do not follow Cisco IOS command syntax and will result in errors. The phrase banner message motd is also not valid; IOS expects the keyword sequence banner motd rather than inserting the word message. The fictional banner login motd command combines two different banner types and is not a standard IOS command.

Common Pitfalls:
A common mistake is to confuse the different banner types and their commands, such as banner motd, banner login, and banner exec. While these all configure banners, the exam question specifically refers to the common Message of the Day banner shown at login, for which banner motd is the canonical command. Another pitfall is forgetting to choose a delimiter that does not appear in the message itself, which can cause configuration issues.

Final Answer:
The correct command is banner motd, which configures a Message of the Day banner displayed when administrators log in.