{{tag>Troubleshooting Legacy Broadband_Routers SIP_ALG DrayTek Vigor}}
====== How to Disable SIP ALG on the DrayTek Vigor Legacy Models (firmware pre-3.8.5)======
SIP ALG (Application Layer Gateway) is a feature which may be enabled by default on most DrayTek Vigor 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 DrayTek Vigor router.

This guide explains how to to disable SIP ALG on the following DrayTek models which are running firmware versions older than 3.8.5:
  * **Vigor 2760**
  * **Vigor 2800**
  * **Vigor 2820**
  * **Vigor 2830**
  * **Vigor 2832**
  * **Vigor 2860**
  * **Vigor 2862**
  * **Vigor 2920**
  * **Vigor 2925**
  * **Vigor 2926**
  * **Vigor 2952**
  * **Vigor 2960**

Even if your particular DrayTek model is not listed, these instructions should still apply if your model is in the same series.

If your DrayTek Vigor router is running firmware version 3.8.5 or newer then please refer to the following guide:
   * [[troubleshooting:sip_alg:draytek_3.8.5]]

  
===== Step-by-Step Guide =====
  - Press the Windows Start button and in the search box type in **cmd** and hit //Enter//
  - Type in\\ <code>telnet 192.168.1.1</code> and hit //Enter//\\ //**Note** Recent versions of Microsoft Windows  may not have **Telnet** installed by default.\\ To install Telnet, click on **Start -> Control Panel -> Programs -> Programs and Features -> Turn Windows Features on or off** -> Ensure **TELNET CLIENT** is checked and click OK.//
  - When prompted, enter your router username and password.\\ //The default username is **admin** and the default password is **admin**//
  - Type in\\ <code>sys sip_alg 0</code>and hit //Enter//
  - Type in\\ <code>sys commit</code>and hit //Enter// to save the newly applied change


====== Further Reading ======
[[http://www.draytek.co.uk/support/guides/kb-sip-alg|SIP ALG on DrayTek Routers]] at at www.draytek.co.uk (registration required to see article).

For information on setting up [[broadband:draytek#quality_of_service_qos|Quality of Service (QoS)]] see [[broadband:draytek#quality_of_service_qos|this guide]].

If you are running firmware version 3.8.5 or newer then please refer to [[troubleshooting:sip_alg:draytek_3.8.5]]