{{tag>Troubleshooting Broadband_Routers SIP_ALG TP-LINK}}
====== How to Disable SIP ALG on the TP-LINK Archer VR900 Modem Router ======
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 [[features:blf|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 VR900** Wireless Dual Band Gigabit VDSL/ADSL2+ Modem Router
  * **TP-LINK Archer VR900** (hardware version 2)

The instructions do differ between different [[#other_tp-link_routers|TP-LINK routers]]. Click [[#other_tp-link_routers|here]] for a list of other TP-LINK routers.
===== Step-by-Step Guide =====
  - {{ :troubleshooting:sip_alg:2017-07-26-tp-link-login-web.png?nolink&800 |}}\\ 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**//
  -{{ :troubleshooting:sip_alg:2017-07-26-tp-link-basic-web.png?nolink&800 |}}\\ On the top menu click **Advanced**
  - On the left, click on **NAT Forwarding**
  - {{ :troubleshooting:sip_alg:2017-07-26-tp-link-natforwarding-web.png?nolink&800 |}}\\ By **SIP ALG** uncheck the box that says Enabled
  - Click **Save**

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

{{topic>TP-LINK&nodate}}
====== Further Reading ======
Further information can be found at [[http://uk.tp-link.com/products/details/cat-15_Archer-VR900.html|TP-Link Archer VR900 Product Page]].