How to Disable SIP ALG on an AT&T Router

Steps to Disable SIP ALG

1. Connect a computer or mobile device to the same network as the AT&T gateway.
2. Open a web browser and navigate to 192.168.1.254, which is the advanced device configuration address for AT&T gateways.
3. Select Firewall from the navigation menu.
4. Select Firewall Advanced.
5. Enter the Device Access Code when prompted. This code is printed on the label attached to the gateway.
6. Locate the SIP ALG setting, turn it off, and click Save to apply the changes.

Once SIP ALG is disabled, reboot your phones and test a call to confirm the issue has been resolved.