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Posted By Gregory

Solving problem with incorrect IP address detection

It's crucial for WP Cerber to detect all IP addresses correctly.


On some web servers, WP Cerber is not able to detect IP addresses automatically due to a non-standard server configuration. That means WP Cerber is unable to protect your website and can even lock you out of your WordPress dashboard.

Most likely your website is behind a proxy

First of all, try to enable My site is behind a reverse proxy in the Main Settings of the plugin and check how the plugin detects IP addresses as described below.

Make sure that WP Cerber detects IP addresses correctly

  1. Open the What is my IP address page in a browser tab (window) and the Access Lists admin page on your website in another browser tab.
  2. Compare the IP address on the What is my IP address page to the IP address under the Your IP label on the Access Lists admin page.
  3. You should see two identical IP addresses. If so, WP Cerber works correctly. Otherwise, follow the next steps below.

What’s next?

If you are still unable to make WP Cerber detect IP addresses correctly, you have to define a special CERBER_IP_KEY constant in the wp-config.php file. The plugin will use it as a key to obtain IP addresses from the $_SERVER variable. See the instruction below.

Configuring the CERBER_IP_KEY constant

  1. Get your current IP address on the What is my IP address page
  2. Go to the Tools admin page which is under the WP Cerber admin menu and click the Diagnostic tab
  3. Scroll down to the Server Environment Variables section
  4. Find your IP address in one of the rows that are displayed in the section
  5. In the first cell of the row with your IP address, you’ll see a key. On the example below, the key is  HTTP_X_REAL_IP
  6. Take that key and add the following line with your key to the beginning of the wp-config.php file (after the line with <?php)
    define('CERBER_IP_KEY', 'HTTP_X_REAL_IP' );
Server Environment Variables

The Server Environment Variables section on the Diagnostic tab

Note: The HTTP_X_REAL_IP is shown as an example, you have to find out and use your own key.

Have any questions?

If you have a question regarding WordPress security or WP Cerber, leave them in the comments section below or get them answered here: G2.COM/WPCerber.


I'm a software engineer and team lead at Cerber Tech. I started coding in 1993 on IBM System/370 and today software engineering at Cerber Tech is how I make my living.

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