Zyxel CX4800-56F Switch: How to Configure a Whitelist for Remote Management to Prevent Unauthorized Access on Zyxel CX4800-CF

This guide demonstrates how to configure a whitelist for remote management access on the Zyxel CX4800-CF switch. A whitelist limits remote access to specific source IP addresses and services, reducing the risk of unauthorized access attempts from unknown devices or networks.

⚠️ Note: All IP addresses and subnet masks in this article are examples. Replace them with actual values from your environment.

Access the Web GUI

1. Log in to the switch's Web GUI using an authorized admin device (e.g., AdministratorPC).
2. Navigate to:
   Menu > Security > Access Control > Remote Management.
3. In the configuration screen:
   • Specify the IP address range that is allowed to access the switch.
   • Select the corresponding management services (e.g., HTTPS, SSH, Telnet, FTP) that each IP or range is permitted to use.
4. Click Apply to save the settings.

Example Configuration & Testing

Assume the following configuration:

• Allowed IP Range: 192.168.10.100 – 192.168.10.120
• Services Allowed: All except HTTP

Test Scenarios

1. PC-1 (192.168.10.100):
   • If accessing the switch via HTTP → Access is denied
   • If accessing via HTTPS (e.g., https://192.168.10.1) → Access is successful
2. PC-2 (192.168.10.200):
   • Not in the allowed range → Cannot access or ping the switch’s management IP
3. AdministratorPC (whitelisted):
   • Can access the switch using all supported remote management services

Troubleshooting

Common Issues:

Overlapping IP Entries:

• If the same IP (e.g., 192.168.10.120) appears in multiple entries with different service permissions, the logic applied is OR.
  → Result: All service types are allowed for that IP.

Administrator Locked Out:

• If all admin devices are removed from the whitelist, the Web GUI becomes inaccessible.
• Solution:
  • Connect via the Console port (if supported) to review or update the configuration.
  • Use CLI to check the whitelist and restore access.

Note: If the Switch does not support Console, please check the manual of your Switch model to find out how to restore the device to factory default settings