SIP ALG (Application Layer Gateway) is a feature which is enabled by default in most D-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 D-Link router.

This guide explains how to disable SIP ALG on most D-Link routers.

1. Fire up a browser (Firefox, Chrome etc) and go to 192.168.0.1 (this is the default IP address on most D-Link routers)
2. Log into the router
   • The default username is usually admin and the default password should be blank
3. Click on Advanced
4. On the left menu click on Firewall Settings
5. Uncheck Enable SPI
6. Set UDP Endpoint Filtering and TCP Endpoint Filtering to Endpoint Independent
7. Under Application Level Gateway (ALG) Configuration uncheck SIP
8. Click Save Settings towards the top of the page
9. If prompted, reboot your router (firewall)
10. Close your browser and restart your handset. SIP ALG is now disabled.

Different D-Link routers may have different instructions. Please refer to the manual specific to your particular D-Link model.

For further information please contact the retailer from whom you purchased your D-Link router.