3xx codes are redirection responses.
They’re not errors as such, but they tell the calling client (User Agent Client, or UAC) that the destination has changed or multiple routes are available.
Correctly handling redirection is critical for ensuring calls don’t drop or loop indefinitely, and for routing traffic efficiently across complex VoIP setups.
Stop your calls from bouncing around or getting lost in redirection loops.
Voyced routes calls precisely and professionally, with full support for clean 3xx handling.
Start routing smarter with Voyced
SIP 3xx Response Codes Explained
300 Multiple Choices
The address resolved to more than one potential destination.
All valid endpoints are listed in the Contact: header or message body.
The client is expected to choose, but not all SIP phones or platforms are capable of doing this automatically.
301 Moved Permanently
The Request-URI is no longer valid. A new address is provided in the Contact: header, and the client should update its local records.
This is similar to a permanent redirect on a website.
302 Moved Temporarily
Similar to 301, but temporary.
Clients are advised to retry at the new address in the Contact: header.
If an Expires: header is included, the redirection can be cached for that period.
305 Use Proxy
The call must be sent through a specific proxy server listed in the Contact: header.
⚠️ Rarely supported and considered obsolete in modern SIP implementations.
380 Alternative Service
The request failed, but other services (e.g. different codecs, methods, or media types) are available.
Details are in the message body. Most UAs do not act on this automatically.
⚠️ Why Redirection Can Fail in Poor SIP Environments
-
Some systems ignore or mishandle 301/302 responses, resulting in failed calls.
-
Clients may not retry alternate
Contact:URIs if 300 is received. -
Platforms that don’t track the state of a redirect can loop or cause duplicate call attempts.
-
Misconfigured proxies might override or block redirects, breaking call routing.
That’s where a professional-grade VoIP provider can make a real difference.
✅ Why Voyced Handles 3xx Better
At Voyced, we’re fully SIP-compliant and built to handle complex routing, whether that involves redirecting calls internally, forwarding users, or handling SIP trunks across countries.
With us, you get:
-
Numbers in 165+ countries, National, Geographic, Toll-Free & UIFN
-
Proper redirection support: 301, 302, 380 fully handled
-
Optional failover routing, call forwarding and IVR trees via Hosted IPPBX
-
Secure, stable SIP trunking with Premium Plus quality
-
Fine-grained control over SIP behaviour, call logic, and trunk rules
-
Real people to support your setup, not just canned responses
3xx codes don’t have to mean confusion
If your calls are dropping, misrouting, or returning unclear errors like “moved temporarily” or “use proxy,” you might not have a redirection-friendly SIP environment.
Make the switch to Voyced
where smart routing, compliant signalling, and clear call flows are part of the standard setup.
Last updated: 01/04/2025
© Voyced
All information provided is copyrighted and purely informative in nature. It is maintained by Voyced with the greatest of care using reliable sources only.
Given the fast evolution of the telecom sector, Voyced does not offer any guarantee about the accuracy and completeness of the information offered.
We explicitly do not give anyone permission to use this information in any other way than to inform themselves about what (legal) requirements there may be and they need to comply with when registering Services and/or DIDs with Voyced.
