Direct upgrades are not always possible depending on your current version:

Connected APs will download the new matching firmware from the controller. They will reboot individually. Track this progress under Wireless > Access Points to ensure all APs return to an "UP" status. Troubleshooting Common Issues

Type y when prompted to confirm the transfer and initiate the firmware decompression. 4. Activating the New Image and Rebooting

Choose TFTP , FTP , or SFTP based on your server.

If you manage your network via Prime Infrastructure, ensure it is compatible with the new WLC software version. 3. Backup Your Configuration

You can perform the upgrade using either the graphical user interface (GUI) or the command-line interface (CLI). Choose the method that best fits your workflow. Method A: Upgrading via the Web GUI (Recommended) to the Cisco WLC GUI via HTTPS. Click on Commands from the top menu. On the left-hand sidebar, select Download File . Configure the following parameters on the download page: File Type: Code Transfer Mode: TFTP, SFTP, or FTP IP Address: The IP address of your file transfer server

GUI: Click at the top right, then go to Commands > Reboot > Reboot . 5. Post-Upgrade Verification and Troubleshooting

The WLC requires an external server to fetch the firmware image file. Set up your transfer protocol beforehand. TFTP vs. SFTP vs. FTP

reset system in <seconds>

Skipping the FUS upgrade will cause the boot process to get stuck in an infinite loop, effectively bricking the controller until you perform a manual recovery. The FUS update updates the controller’s bootloader and underlying hardware initialization code.

(Cisco Controller) >config ap cert-expiry-ignore ssc enable (Cisco Controller) >config ap cert-expiry-ignore mic enable

The Cisco 2500 WLC maintains two software images in its onboard flash memory: the image and the Backup image. When you download new firmware, it automatically overwrites the backup slot. Verify the Boot Order