SIP 380 Alternative Service
What SIP 380 means
The call did not succeed as asked, but an alternative is offered. In UK deployments this most often appears around emergency call handling and where a platform redirects a request to a different service.
What SIP 380 Alternative Service actually means
The call was unsuccessful but an alternative service is available, described in the message body. It is unusual in that the response carries a suggestion rather than only a refusal, which is why the body matters more than the code.
What causes SIP 380 on a business phone system
- Emergency call handling redirects the requestPlatforms handle emergency calls specially and may answer with an alternative service. Worth knowing about because emergency calling on VoIP has to be configured deliberately.
- The platform offers a different route for the requestWhere a service has moved, an alternative may be offered rather than the call simply failing.
How to fix SIP 380
- Read the alternative offered in the message bodyThe body describes what to use instead, which is the actionable part of the response.
- Verify emergency call configurationIf this appears on emergency dialling, confirm your registered address and emergency routing are correct with your provider. This is a compliance matter as much as a technical one and should not be left unresolved.
Fixing the underlying problem
This page explains the code. These guides walk through the fix in detail.
Questions about SIP 380
What does SIP 380 Alternative Service mean?
The call failed as requested, but the server is offering something else instead, described in the message body. In UK hosted VoIP it turns up most often around emergency call handling, which is worth verifying with your provider if you see it there.
Related SIP response codes
Source. SIP 380 Alternative Service is defined in RFC 3261 section 21.3.5 and registered in the IANA SIP Parameters — Response Codes. The causes and fixes above are drawn from our own experience supporting UK business phone systems.