How to Upgrade Firmware on a Zyxel Switch Stack System

Firmware upgrades are essential for maintaining the stability, security, and performance of your Zyxel switch stack. If your switches are managed through Nebula, firmware upgrades can be performed directly from the Nebula Control Center (NCC), allowing centralized management of the entire stack. Alternatively, firmware can also be upgraded through the local web interface of the stack master switch.

This article describes both methods, starting with firmware upgrades through Nebula and then covering the local web interface procedure.

• All switches in the stack should run the same firmware version to ensure stack compatibility and proper operation.
• Stacking is supported only between switches of the same model and firmware version.
• Firmware upgrades can be managed centrally from the stack master switch.
• In Stacking mode, the Slot selector allows administrators to upgrade an individual stack member or all stack members simultaneously.
• Zyxel switches support dual firmware images (Firmware 1 and Firmware 2), allowing one image to be used as the active firmware and the other as a backup.
• A newly uploaded firmware image does not become active immediately. The switch stack must be rebooted using the selected boot image before the new firmware takes effect.
• After the upgrade is completed, verify that all stack members are running the expected firmware version.

Note: Before performing a firmware upgrade, ensure that the correct firmware package for the switch model has been downloaded and extracted. Using an incorrect firmware image may prevent the device from operating properly.

Upgrade Firmware Through the Web GUI

1. Log in to the stack master switch's web interface.
2. Navigate to MAINTENANCE > Firmware Upgrade > Firmware Upgrade.
3. Verify the current firmware version of all stack members in the Version table.
4. In the Firmware section, select the target slot or All to upgrade all switches in the stack.
5. Choose the target firmware image (Firmware 1 or Firmware 2), click Choose File, and select the downloaded firmware file.
6. Click Upgrade to upload the firmware.
7. After the upload is complete, select the desired boot image under Config Boot Image and click Apply.
8. Reboot the stack to activate the new firmware.

In this example, the firmware image was uploaded to Firmware 1 with the All option selected. As shown below, Firmware 1 on both Slot 1 and Slot 2 has been updated to the new version, while Firmware 2 still contains the previous firmware image. 

Before proceeding with the upgrade of Firmware 2, save the current configuration to Configuration 2 (Config 2). This ensures that the stack can boot using the updated firmware image and the corresponding configuration after the reboot.

After the upload finishes, verify that the new firmware image has been successfully written to the selected firmware partition.

You can also connect to the stack master switch through a terminal emulator such as PuTTY and use the following command:

show stacking slot <ID>

Example:

show stacking slot 2

In the output, check the FaOS Version section and verify that the selected firmware image (Flash 1 or Flash 2) displays the expected firmware version.

FaOS Version
  Running : V2.00(ACJN.1)20260608
  Flash 1 : V2.00(ACJN.1)20260608
  Flash 2 : V2.00(ACJN.1)20260608

Once the firmware version has been verified, return to the Web GUI and reboot the stack using the desired boot image (Firmware 1 or Firmware 2) to activate the new firmware.