On a Cisco router, you type Router# sh ru and receive the error message % ambiguous command. Why is this message displayed?

Introduction / Context:
Shortened commands and abbreviations are a convenient feature of Cisco IOS. However, these abbreviations must be unique so that IOS can determine exactly which full command you intend. When an abbreviation matches more than one possible command, IOS generates an ambiguous command error. Understanding this behaviour is important for troubleshooting command line issues in labs and production networks.

Given Data / Assumptions:

• You are in privileged EXEC mode, as shown by the Router# prompt.
• You enter the command sh ru, intending to run show running-config.
• IOS responds with % ambiguous command, indicating that the router cannot determine a single matching command.
• The router has multiple show commands whose names begin with ru.

Concept / Approach:
Cisco IOS allows you to abbreviate commands as long as the abbreviation is unambiguous. For example, sh run is commonly used for show running-config because no other show command begins with run. However, the shorter abbreviation sh ru might match more than one show keyword, such as running-config and route or rusers on some systems. When IOS sees that ru could refer to multiple valid completions, it flags the input as ambiguous instead of guessing which command you wanted.

Step-by-Step Solution:
Step 1: The user types sh ru at the Router# prompt.Step 2: IOS parses the input and identifies sh as an abbreviation for show.Step 3: IOS then examines subcommands that begin with ru and discovers that more than one show command keyword starts with these characters.Step 4: Because the abbreviation ru is not unique, IOS cannot resolve it to a single command such as running-config.Step 5: IOS returns the error % ambiguous command to instruct the user to type more characters to make the command unique, for example sh run.

Verification / Alternative check:
You can type show ? at the router prompt to view all available show subcommands. By looking at the list, you will see several entries that begin with ru, which confirms why IOS treated sh ru as ambiguous. Typing show run works because run is long enough to be unique.

Why Other Options Are Wrong:
Option A suggests that more parameters are needed, but IOS uses different messages when options or arguments are missing.Option C is incorrect because show running-config definitely exists as a valid command.Option D is wrong because show running-config is appropriate in privileged EXEC mode, not in configuration mode.Option E incorrectly blames the IOS image; command ambiguity is a normal behaviour, not a sign of corruption.

Common Pitfalls:
Many learners assume that any short form of a command will always work. In practice, you must include enough characters to uniquely identify the command. When you see % ambiguous command, the solution is usually to type more of the keyword, not to change modes or reboot the router.

Final Answer:
The message appears because There is more than one show command that starts with the letters ru, so the abbreviation sh ru is not unique.