Configure Watchguard firewall for SIP VOIP, Disable SIP ALG
Posted by Chris P. on 05 April 2019 12:17 PM

You can verify if your router is SIP ALG ENABLED by downloading and running our SIP ALG TESTER Program

SIP ALG Tester Download


Step 1: Create a “Static NAT (SNAT)”

First, the Static NAT must be configured in order to forward the incoming traffic from the Static Public IP, to the local IP of the PBX:

1. Navigate under Firebox® UI > Firewall > SNAT and click “Add”

2. In this example the name “VANTACT_SNAT” is given to the SNAT Policy.

3. Select Static NAT.

4. Under SNAT Members click “Add”

5. Select the “External Static IP” under the drop-down menu. In this example the external IP of the device is which should be used to NAT inbound trac to the PBX.

6. Enter the Internal/Private IP address of the PBX and click OK (in this example the internal/private IP of PBX is

7. Click “Save” and the SNAT Policy is now active.

Step 2: Create Firewall Policy After setting up the static NAT, a Firewall Policy must be configured:

1. Navigate under Firebox® > Firewall > Firewall Policies and click “Add Policy”

2. In this example the name “VANTACT_Services” is given to the Policy Name.

3. As a “Policy Type” select “Custom” and click “Add.”

4. In this example the name “VANTACT_Ports” is given to the “Policy Template”

5. Use the “Add” button below the “Protocols” to add a custom list of ports which shall be allowed to connect to the PBX.  (Vantact ports SIP: 5060-5061 TCP, RTP: 40000-65000 UDP)

6. “Single Port” or “Port Range” can be selected. When all ports are set, click “Save”

7. Remove the “From” and “To” objects.

8. Under “From” click “Add”

9. Under the drop-down menu select “Any External” and “OK”

10. Under “To” click “Add” 11. Under the drop-down menu select “Static NAT”

12. The SNAT created previously, will be listed (in this example “ VANTACT_SNAT”). Select the SNAT and “OK”

13. The Firewall policy should look like the screenshot below:


Note: In this example, “Any External” is used, therefore any host can establish a connection on the public IP Address of the PBX. In case the source of the incoming trac must be limited you can create a group of allowed IPs to be allowed under “From.”