SIP 480 Temporarily Unavailable
The callee is known but not reachable right now, for example not registered or busy with do-not-disturb.
4xx Client failure · RFC 3261 · Answer to OPTIONS: Up. It doesn't have the address we asked for available.
What SIP 480 means
A 480 says the callee exists and the server knows it, but it can't take the request right now. The device may not be registered, the user may have set do-not-disturb, or the call went unanswered. The server may add a Retry-After header with a better time to try again.
480 is common on INVITEs to extensions and to numbers behind a PBX. Gateways also produce it for the phone network: RFC 3398 maps Q.850 cause 19, no answer from user, to 480, along with cause 20, subscriber absent, and cause 31, normal unspecified. Because the condition is temporary, a later call may well succeed.
Example response
SIP/2.0 480 Temporarily Unavailable
Via: SIP/2.0/UDP 198.51.100.23:5060;branch=z9hG4bK-480-q5
From: <sip:+[email protected]>;tag=0f4d
To: <sip:+[email protected]>;tag=tu-28
Call-ID: [email protected]
CSeq: 4 INVITE
Retry-After: 300
Reason: Q.850;cause=19;text="No answer from user (user alerted)"
Content-Length: 0Common causes of SIP 480
- The phone or softphone for the extension isn't registered, for example after a network change or a reboot.
- The user has set do-not-disturb, and the PBX answers calls with 480 instead of sending them to voicemail.
- The call rang without being answered, and the PBX ended it with 480.
- The phone network reported no answer, subscriber absent or an unspecified clearing, all of which map to 480.
- A hunt group or queue had no member available to take the call.
How to fix SIP 480
- Check the registration state of the target device; an expired or missing registration is the first thing to rule out.
- Look at the do-not-disturb and forwarding settings for the extension or number.
- Read Retry-After and the Reason header to see whether the far end or the phone network produced the 480.
- Make sure unanswered calls go to voicemail or a fallback, so callers don't get a hard failure.
SIP 480 as an answer to OPTIONS
A 480 to OPTIONS means the server is up, but the address in the probe isn't available right now. SBCs sometimes answer this way for a user or domain they know but can't serve at the moment. A PingVo Route counts it as reachable by default.
Questions about SIP 480
What is the difference between SIP 480 and 404?
404 means the user doesn't exist at this server. 480 means the user exists but can't be reached right now, so trying again later can work.
What is the difference between SIP 480 and 486?
486 says the callee is reachable but busy. 480 says the callee can't be reached at all for the moment, for example because no device is registered.