SIP ALG (Application Layer Gateway) is a feature which is enabled by default on most BT Business Hub 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.

For our Hosted VoIP service, including out Single User services, SIP ALG must be disabled on your BT Business Hub router.

This article explains how to disable SIP ALG on the BT Business Hub modem router. This router is generally supplied by BT to business customer.

Although this guide was written with the BT Business Hub 5 router in mind, the guide below should be applicable to similar BT Business Hub routers.

1. Fire up a browser (Firefox, Chrome, Opera etc) and go to 192.168.1.254
   This is the default router IP address. Your router's IP address may be different.
2. Click on Advanced Settings
3. Enter the admin password.
   The default password can be found on the bottom of the BT Business Hub or on the plastic card you can pull out from behind the Hub.
4. Click on Continue to Advanced Settings
5. Click on Firewall then Configuration and scroll down to Application Layer Gateway
6. Beside Disable SIP ALG select Yes and click Apply

The BT Business Hub has been known to expose your handsets to the Internet. You may experience random 'phantom' phone calls, possibly at inconvenient times. This will be due to hackers scanning your network.

SureVoIP can not be held responsible for costs incurred where compromised equipment has been used fraudulently or otherwise misused.

We suggest purchasing a router more suitable for business use with a better security track record, such as a DrayTek router. Contact us and we will be happy to provide a quote.

This article is applicable to the BT Business Hub only. If you were looking for the BT Home Hub then click here.

Further information can be found at BT Business support page.