How to Re-enable a Disabled LAN Interface on Zyxel firewall using CLI

Zyxel_Melen

This FAQ guide explains how to re-enable a LAN interface on a Zyxel firewall that was accidentally disabled through the graphical user interface (GUI). This guide assumes you do not have SSH web access enabled and need to use the Command Line Interface (CLI) through a console connection.

# Scenario

You have accidentally disabled the LAN1 interface on your Zyxel firewall through the GUI. As a result, devices connected to the LAN1 port can no longer access the network or the internet. You need to re-enable the LAN1 interface to restore connectivity.

# Re-enabling the LAN Interface

Follow these steps to re-enable the LAN interface using the CLI:

1. Connect to the USG's console port

 Using a console cable and a terminal emulator on your computer.

2. Log in

 Log into the USG using your admin credentials.

3. Verify the disabled interface:

- Use the command `show interface all` to list all interfaces and their current status. Identify the disabled interface (e.g., "lan1") and note its status ("Inactive" or "Down").

4. Enter configuration mode:

- Type `configure terminal` and press Enter.

5. Access the interface configuration:

- Type `interface lan1` (replace "lan1" with the actual name of the disabled interface) and press Enter.

6. Re-enable the interface:

- Type `no shutdown` and press Enter.

7. 

Verify the change:

- Type `exit` twice to return to the privileged EXEC mode.

- Run `show interface all` again to verify that the LAN interface is now "Up".

# Additional Information:

* Identifying the correct interface name:

 The `show interface all` command will display a list of all interfaces, including their current status and assigned IP addresses. Carefully review the output to identify the correct interface name before proceeding.

* CLI Reference Guide:

 For more detailed information on Zyxel firewall CLI commands, please refer to the official CLI Reference Guide for your specific firewall model. This guide can be found on the Zyxel website.