If you cannot access a Zyxel Firewall by any management method, the first recommended step is to perform a simple restart by powering the device off and then on again. A reboot may resolve temporary system issues without affecting the current configuration. If the device remains inaccessible after a reboot, or if the administrator credentials are lost, the device can be reset to its factory-default settings.
This article is based on USG FLEX 200 as a reference model. However, the described reboot and reset procedures are generally applicable to other Zyxel firewall models, including VPN, USG, ATP, and USG FLEX series devices.
ATP100 / ATP100W / ATP200 / ATP500/ ATP700/ ATP800 USG FLEX 50 / USG FLEX 50W/ USG FLEX 100 USG FLEX 100W / USG FLEX 200 / USG FLEX 500 USG FLEX 700
Important:
Although the procedures are similar across multiple Zyxel firewall models, LED behavior and reset mechanisms may vary depending on the specific model and firmware version.
Always refer to the User’s Guide of the exact model before performing any reboot or factory reset operation.
Reboot Procedures Zyxel Firewall
| 1. Reboot via Web GUI | 2. Reboot via CLI | 3. Reboot via ZON Utility |
Action: Result:
| The Zyxel firewall can also be rebooted using the CLI command: This performs a normal system restart without removing configuration settings. | When the device is reachable in the same network, ZON Utility can be used. Action: Result:
|
Resetting Zyxel Firewall
Use the following procedure to reset the Zyxel Device to its factory-default settings. This overwrites the settings in the startup-config.conf file with the settings in the system-default.conf file.
Hardware Factory Reset using RESET Button
This is the primary and recommended method when the device is inaccessible or credentials are lost.
Procedure:
Make sure the device is powered on.
Confirm that PWR and SYS LEDs are ON and not blinking.
Press and hold the RESET button.
Keep holding the button for approximately 5 seconds, until the SYS LED starts blinking.
Release the RESET button.
Wait for the device to reboot automatically.
Result:
The current configuration is removed
Factory default configuration is loaded
Default access settings are restored
You should be able to access the Zyxel Device using the default settings.
Factory Reset via ZON Utility
If Web GUI access is not possible but the device is reachable on the network:
Action:
Select the device → click Reset Configuration to Default
Result:
Configuration is erased
Device returns to factory default state
CLI command to Reset Zyxel Firewall
Router > apply /conf/system-default.conf
Factory Reset during Nebula Mode Change
In specific Nebula management scenarios, the device may reset automatically.
Examples:
Removing the device from a Nebula organization
Switching from Cloud Monitoring Mode to Nebula Mode
In some cases, a manual RESET button press is required to complete the factory reset.
LED Light Indication during Reboot and Reset
The User’s Guide and official Zyxel Support documentation describe LED behavior mainly using the SYS LED.
Only the indications explicitly documented are listed below.
LED Indication Table
| LED Indicator | State | When it occurs | Meaning / Description |
|---|---|---|---|
| PWR | On (steady) | Before factory reset | Device is powered on; required condition before pressing RESET |
| SYS | On (steady) | Before factory reset | System is operating normally; reset can be initiated |
| SYS | Begins blinking | RESET button held (~5 seconds) | Factory reset process has been triggered |
| SYS | Blinking | During reset or reboot | Device is performing a system operation (do not power off) |
| SYS | Blinking → steady On | After reset/reboot | Operation completed successfully; device is ready |
| SYS | Blinking | During Nebula USB provisioning | Device is processing Nebula configuration from USB |
| SYS | On again | After Nebula provisioning | Nebula registration completed successfully |
Important Notes
Do not disconnect power while the SYS LED is blinking.
Factory reset is confirmed only when the SYS LED starts blinking, not by the time the RESET button is pressed.
The documentation does not define LED colors or detailed behavior for LAN/WAN LEDs during reset or reboot.
Only LED behavior explicitly documented by Zyxel is included to avoid misinformation.
Summary
Reboot is used for maintenance and troubleshooting without data loss.
Factory reset permanently removes the current configuration.
SYS LED behavior is the primary indicator for reset and reboot processes.
Always wait for the SYS LED to return to a steady state before accessing the device.
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