Skip to main content

Ep 03: Cisco IOS Error Messages

If you kinds find this course useful and want 10% off your first year, use our link to sign up for 10% off!

Cisco IOS Error Messages​

In this episode, we focus on reading Cisco IOS error messages, understanding the ^ marker, identifying incomplete commands, and using the do command from Global Configuration mode according to the official CCNA 200-301 certification blueprint.

Learning Objectives​

  1. Trigger the typo error and read the ^ marker
  2. Give IOS half a command — then finish it
  3. Run a show command from config mode with do

Trip the typo error and read the ^ marker​

Nobody learns the Cisco IOS CLI without eventually making a typo. The good news is that IOS gives you useful information when you enter a command incorrectly.

We are going to intentionally create an error so you can learn how to recognize it. When you first connect to the switch, you will start in User EXEC mode.

Switch>

To reach Privileged EXEC mode, type enable or en for short.

Switch> enable
Switch#

Now we will intentionally misspell the show running-config command. Type shwo running-config and press Enter.

Switch# shwo running-config
             ^
% Invalid input detected at '^' marker.

The % Invalid input detected at '^' marker. message tells us that IOS does not understand part of the command we entered. The ^ marker points to the location where IOS detected the problem.

📌

Key Concept To Remember For The CCNA

When you see % Invalid input detected at '^' marker., look directly above the ^ marker to identify where IOS detected the invalid input. This can help you quickly find and correct a typo or incorrect command.

Now fix the typo and enter the correct command.

Switch# show running-config

The command should now run successfully and display the switch's active configuration.

Give IOS half a command — then finish it​

The next error is different. Instead of entering a command IOS does not understand, we are going to enter a command that IOS does understand but leave out information that the command requires.

First, enter Global Configuration mode.

Switch# configure terminal
Switch(config)#

Now type hostname by itself and press Enter.

Switch(config)# hostname
% Incomplete command.

% Incomplete command. means that IOS recognizes the command, but you have not provided all of the information required to complete it.

The hostname command requires a name to be entered after the command. Finish the command by entering hostname Sandbox-SW1.

Switch(config)# hostname Sandbox-SW1
Sandbox-SW1(config)#

Notice that the prompt changes immediately to Sandbox-SW1(config)#. This confirms that the hostname has been changed.

📌

Do not Forget!

% Incomplete command. is different from % Invalid input detected at '^' marker. An incomplete command is a valid command that is missing required information. An invalid input error means IOS does not recognize the input at that location.

Run a show command from config mode with do​

While you are in Global Configuration mode, try entering the show running-config command.

Sandbox-SW1(config)# show running-config
             ^
% Invalid input detected at '^' marker.

The problem is not that show running-config is an invalid command. The problem is that show commands normally run from EXEC mode, while we are currently in Global Configuration mode.

Instead of leaving configuration mode, you can use the do command to run an EXEC-mode command from Global Configuration mode.

Sandbox-SW1(config)# do show running-config

The command will now display the running configuration while keeping you in Global Configuration mode.

Look through the output and find the hostname that we configured earlier.

!
hostname Sandbox-SW1
!

The do command is especially useful when you need to verify a configuration change without leaving the configuration mode you are currently working in.

📌

Key Concept To Remember For The CCNA

The do command allows you to execute EXEC-mode commands while you are in a configuration mode. For example, do show running-config lets you view the running configuration without first leaving Global Configuration mode.

IOS Does Not Care About Capitalization​

One final thing to remember is that Cisco IOS commands are not case-sensitive. Capitalization will not cause an error.

For example, these commands are treated the same by IOS:

Configure Terminal
configure terminal
CONFIGURE TERMINAL

The same applies to show commands:

SHOW VERSION
show version
Show Version

The important errors to recognize are the three we practiced in this episode: invalid input, incomplete commands, and attempting to use an EXEC-mode command from the wrong configuration mode.

⚠️

Always read Cisco IOS error messages carefully instead of immediately trying another command. The error message and the ^ marker often tell you exactly what needs to be corrected.

Follow The Rest Of The Series Here​

CCNA Master Guide

Follow Us on Social Media​

YouTube
Discord
Apparel
Patreon
Reddit
Rumble