How do I downgrade firmware for an ATP Series Firewall?

Zyxel_Stanley

Question:
How do I downgrade firmware for an ATP Series Firewall?

Answer:
Newer firmware may include new CLI commands, so downgrading can cause configuration apply failures.

1. Before downgrading, backup the current startup-config file.
2. In the firewall local WebGUI, go to Maintenance > File Manager > Firmware Package, upload the target older firmware, set it as the next boot image, and reboot.
3. After the device boots on the older firmware, first upload the backup config, then run apply config through CLI.
   e.g. Router> apply /conf/1010backup-config.conf ignore-error