Air-ct2500-k9-2-0-0-0-fus.aes [hot] May 2026

The file air-ct2500-k9-2-0-0-0-fus.aes is a critical system file for the Cisco 2504 Wireless LAN Controller (WLC). Specifically, it is a Field Upgrade Software (FUS) image.

• Backup configurations: Before upgrading the firmware, backup the wireless controller's configuration to prevent data loss.
• Use a stable power source: Ensure the wireless controller has a stable power source during the firmware upgrade process.
• Monitor the upgrade process: Closely monitor the firmware upgrade process to detect any issues or errors.

• Re‑verify AP join status.
• Check for any configuration mismatches (especially if jumping from a much older release).
• If planning to go to a modern release (e.g., 8.5.x or 8.10.x), you may need this FUS as an intermediate step before upgrading further.

Before you start