SIP ALG (Application Layer Gateway) is a feature which is enabled by default in most TP-LINK routers and inspects VoIP traffic as it passes through and modifies the messages on-the-fly.

In few situations this is useful, but in most situations SIP ALG can cause problems using the service. Very often, SIP ALG is poorly implemented causing VoIP messages to be modified in a harmful way or simply corrupts them. In such cases you may experience issues registering your handset, one-way or no audio, unable to receive calls, and issues with Busy Lamp Field (BLF) and Message Waiting Indicators (MWI).

For our Hosted VoIP service, including out Single User services, SIP ALG must be disabled on your TP-LINK router.

This guide explains how to disable SIP ALG on the following models:

• TP-LINK Archer D7 AC1750 Wireless Dual Band Gigabit ADSL2+ Modem Router
• TP-LINK Archer D2 AC1750
• TP-LINK Archer D7 AC750
• TP-LINK TD-W8968 (hardware version 2)
• TP-LINK TD-W8970 (hardware version 3)
• TP-LINK TD-W8980 N600
• TP-LINK TD-W9980 N600

For other TP-LINK routers not in the list above click here.

1. Fire up a browser (Firefox, Chrome etc) and go to 192.168.1.1 (this is the default IP address)
   The default username is admin and the default password is admin
2. On the left, click on Network and then click on ALG Settings
3. By SIP ALG select Disable
4. Click Save

Different TP-LINK routers may have different instructions. Please see list below for instructions for your particular device.

Further information can be found at TP-Link Archer D7 User Guide.