SIP 181 Call Is Being Forwarded vs 482 Loop Detected
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 482 (Loop Detected) is a 4xx Client Failure response. 181 indicates that a proxy server may send this to indicate that the call is being forwarded to a different set of destinations. In contrast, 482 means that the server has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
Description
A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
When You See It
When the callee has call forwarding enabled and the request is being redirected to another number or device.
How to Fix
No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings.
Description
The server has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
When You See It
When routing configuration causes a request to cycle between two or more proxies without reaching the callee.
How to Fix
Review proxy routing tables and DNS records. Check for circular references in SIP routing. Fix the routing configuration to break the loop.
Key Differences
181 is a 1xx Provisional response, while 482 is a 4xx Client Failure response.
SIP 181: A proxy server may send this to indicate that the call is being forwarded to a different set of destinations.
SIP 482: The server has detected a loop. The request was received with its own address in the Via header, indicating it has been forwarded back to itself.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 482 when when routing configuration causes a request to cycle between two or more proxies without reaching the callee.
When to Use Which
For 181 (Call Is Being Forwarded): No action needed. The call is being redirected. If forwarding is unintended, the callee should update their forwarding settings. For 482 (Loop Detected): Review proxy routing tables and DNS records. Check for circular references in SIP routing. Fix the routing configuration to break the loop.