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VoIP Compatibility with Arris Comcast Xfinity TG852G Gateway: Disabling SIP ALG

The Arris Comcast Xfinity TG852G Gateway is a widely used modem-router combo that offers both internet and VoIP services. While it's designed to support VoIP, users often encounter compatibility issues, primarily due to the SIP ALG (Session Initiation Protocol Application Layer Gateway) feature. This article explores why the TG852G may not work optimally with VoIP services and provides a step-by-step guide on disabling SIP ALG to enhance VoIP compatibility.

Understanding VoIP Compatibility Issues with the TG852G

VoIP and the TG852G

The TG852G integrates internet and VoIP services, aiming to provide a seamless communication experience.
However, compatibility issues can arise due to firmware, network settings, or specific router features like SIP ALG.

The Role of SIP ALG

SIP ALG is designed to assist VoIP traffic in passing through the router's NAT (Network Address Translation).
It modifies VoIP traffic to comply with NAT requirements, which, in theory, should aid in the smooth delivery of VoIP packets.

Common Issues Caused by SIP ALG

Interference with VoIP signaling, leading to problems like call drops, one-way audio, or difficulties in initiating calls.
Inconsistencies in handling VoIP packets, resulting in poor call quality and connectivity.

Disabling SIP ALG on the Arris Comcast Xfinity TG852G

Disabling SIP ALG is often recommended to resolve these VoIP-related issues. Here's how to do it:

Accessing the TG852G Settings

Connect to Your Network: Use a computer connected to the TG852G network.
Open a Web Browser: Enter the gateway’s IP address, typically or
Log In: Use your administrator username and password.

Navigating to SIP ALG Settings

Go to Advanced Settings: After logging in, find the 'Advanced' section in the router settings.
Find NAT or Firewall Settings: SIP ALG settings are usually under these sections.

Disabling the SIP ALG Feature

Locate SIP ALG: Look for an option labeled ‘SIP ALG’, ‘ALG Configuration’, or similar.
Disable SIP ALG: Uncheck the box or toggle the switch to ‘Off’.
Save Changes: Ensure you save your new settings.
Reboot the Router: Restart the TG852G to apply changes.


VoIP compatibility issues with the Arris Comcast Xfinity TG852G Gateway are often attributable to the SIP ALG feature. Disabling SIP ALG can enhance VoIP performance, leading to clearer calls and more reliable connections. Remember, while SIP ALG is meant to facilitate VoIP services, it often hinders them instead. Adjusting your router settings accordingly can significantly improve your overall VoIP experience

Updated on: 01/22/2024