Disabling SIP-ALG
SIP-ALG is not recommended for use with CircleLoop. This article explains what SIP-ALG is, how it can affect your calls, and why it should be disabled.
What is SIP-ALG?
SIP-ALG (Session Initiation Protocol - Application Layer Gateway) is a feature found on many routers.
It allows the router to inspect and rewrite SIP messages sent between SIP desk phones. While it is designed to assist SIP devices communicating outside the local network, it can interfere with how SIP signalling works.
Most routers that support SIP-ALG have it enabled by default.
To use a SIP desk phone with CircleLoop, SIP-ALG must be disabled.
How SIP-ALG can affect your calls
If SIP-ALG is enabled, you may experience:
- Call Receiving, Dropped Calls, and Failed Call Transfers
Calls may not come through, or be dropped when answered. You won’t be able to transfer calls, put calls on or off hold, or park calls.
- Unable to register or Non-Functioning Call Groups
Certain devices fail to register on to the CircleLoop platform or are incapable of receiving data. Phones in call groups won’t ring as required.
- Direct-to-Voicemail
Inbound calls may be directed straight to voicemail or receive and error message and the call cut off.
If you're experiencing any of the above issues, we recommend checking whether your router supports SIP-ALG, and if so, confirm that the feature is disabled.
How to disable SIP-ALG?
The exact steps depend on your router manufacturer.
In most cases, the setting can be found within:
-
Advanced settings
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Network settings
-
NAT settings
It is usually presented as a toggle or checkbox.
Please refer to your router manufacturer’s documentation for specific instructions on how to disable SIP-ALG.