SIP 181 Call Is Being Forwarded vs 502 Bad Gateway
SIP 181 (Call Is Being Forwarded) is a 1xx Provisional response, while 502 (Bad Gateway) is a 5xx Server 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, 502 means that the server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
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, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
When You See It
When a SIP proxy receives a malformed or invalid response from the next-hop server. Common in interop scenarios between different vendors.
How to Fix
Check the downstream server's health and configuration. Verify SIP message formatting between the two servers. Review network connectivity.
Key Differences
181 is a 1xx Provisional response, while 502 is a 5xx Server 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 502: The server, acting as a gateway or proxy, received an invalid response from a downstream server it accessed in attempting to fulfill the request.
You encounter 181 when when the callee has call forwarding enabled and the request is being redirected to another number or device.
You encounter 502 when when a SIP proxy receives a malformed or invalid response from the next-hop server. Common in interop scenarios between different vendors.
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 502 (Bad Gateway): Check the downstream server's health and configuration. Verify SIP message formatting between the two servers. Review network connectivity.