Cisco – Configuration Not Saved After Power Off

Posted on by

If you’ve ever encountered a situation where your Cisco router loses its configuration and reverts to factory settings after a power cycle, you’re not alone. This issue can be frustrating, especially if you spent time carefully configuring the device. Let’s dive into why this happens and how to resolve it.

Why Does This Happen?

The problem often lies in the configuration register value. Cisco routers use this register to determine how they boot and whether to load the saved configuration from memory. If the configuration register is set to 0x2142, the router will bypass the startup configuration, essentially behaving as if it has been reset to factory defaults.

This setting is commonly used when resetting a router to factory defaults but can cause issues if not changed back after reconfiguration.

How to Diagnose the Problem

1. Check the Configuration Register

Use the following command to view the current register setting:

show version

At the bottom of the output, you should see a line like this:

Configuration register is 0x2142

If the register is set to 0x2142, your router will ignore the saved configuration on startup, leading to the issue.

How to Fix the Problem

To resolve this, you need to update the configuration register to the correct value (0x2102), which tells the router to load the saved configuration on startup. Follow these steps:

  1. Access the Router’s Command Line
    Connect to the router using a console connection or SSH.
  2. Enter Privileged EXEC Mode
    Run the command:
    enable
  3. Enter Global Configuration Mode
    Run the command:
    configure terminal
  4. Update the Configuration Register
    Set the register to 0x2102 with the following command:
    config-register 0x2102
  5. Exit Configuration Mode
    Run the commands:
    end
    write
  6. Reboot the Router
    Power off the router and turn it back on. The router should now load the saved configuration on startup.

Additional Notes

  • Saving Your Configuration: Always ensure your running configuration is saved to the startup configuration using the command:
    write memory
    or
    copy running-config startup-config
  • Testing the Change: After making these changes, power off the router and turn it back on to confirm the issue is resolved. Verify the configuration is loaded properly by checking the router’s settings.

Preventive Measures

  1. Double-Check Register Settings: After resetting a router to factory defaults, ensure the configuration register is set back to 0x2102 if you plan to use the device in a normal environment.
  2. Save Regularly: Periodically save your configuration to avoid losing critical settings.
  3. Backup Configurations: Maintain backups of your configurations externally, either via TFTP or local storage, for quick recovery.

By ensuring the configuration register is set correctly, you can avoid unnecessary headaches and ensure your router retains its settings after a power cycle.