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February 23, 2024
NAT Issues

FreePBX is an open-source VoIP (Voice over Internet Protocol) phone system based on Asterisk. NAT (Network Address Translation) and Firewall issues can often cause problems with the proper functioning of FreePBX. These issues may result in call quality problems, registration failures, and other communication-related difficulties. This instruction manual will guide you through the process of identifying and resolving NAT and Firewall issues with FreePBX.



Step 1: Identifying NAT and Firewall Issues: Before proceeding with the fix, it’s essential to verify whether NAT and Firewall issues are causing the problems. Some common symptoms include:



  1. One-way or no audio during calls.
  2. Frequent call drops or call quality problems.
  3. Phones unable to register or remain registered with the FreePBX server.
  4. Difficulty making or receiving calls to/from external networks.

Step 2: Check Firewall Settings:



  1. Access your FreePBX server’s administration interface through a web browser.
  2. Navigate to the “Admin” menu and select “Firewall.”
  3. Make sure the firewall is enabled, and the necessary SIP and RTP ports are open. Common SIP ports are 5060 (UDP/TCP), while RTP uses a range of UDP ports (e.g., 10000-20000).
  4. If you are using a separate network firewall (external to FreePBX), ensure that the required ports are forwarded to your FreePBX server’s internal IP address.

Step 3: Configure SIP Settings:



  1. In the FreePBX administration interface, go to the “Settings” menu and select “Asterisk SIP Settings.”
  2. Under the “Chan SIP Settings” tab, locate the “NAT Settings” section.
  3. Set “NAT” to “Yes” if your FreePBX server is behind a NAT gateway. If your server has a public IP address, set it to “No.”
  4. If you are unsure about the external IP address, you can set “External IP” and “Local Network” fields manually. Otherwise, FreePBX should auto-detect this information correctly.
  5. Save the changes.

Step 4: Adjust RTP Settings:



  1. In the FreePBX administration interface, go to the “Settings” menu and select “Asterisk SIP Settings.”
  2. Under the “Chan SIP Settings” tab, locate the “RTP Settings” section.
  3. Set the “RTP Symmetric” option to “Yes” if your network requires symmetric RTP. Otherwise, set it to “No.”
  4. Save the changes.

Step 5: Configure Extensions:



  1. For each SIP extension, navigate to “Applications” and select “Extensions.”
  2. Choose the extension you want to configure, or create a new one if needed.
  3. Under the “NAT Settings” section, set “NAT” to “Yes” if the extension is connecting from a NATed network. Otherwise, set it to “No.”
  4. Save the changes.

Step 6: Restart Services:



  1. After making the necessary configuration changes, it’s crucial to restart the FreePBX services to apply the modifications correctly.
  2. Go to the “Admin” menu and select “Asterisk CLI.”
  3. In the command-line interface, type core restart gracefully and press Enter. Wait for the services to restart.

Step 7: Test the Configuration:



  1. After the server restarts, test your FreePBX system to ensure that NAT and Firewall issues are resolved.
  2. Make test calls to check for audio quality and two-way audio.
  3. Verify that SIP extensions can register successfully and remain registered.

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