486 4xx Client error RFC 3261
SIP 486 Busy Here
The callee was contacted but is busy at this endpoint. The caller may try again later or another location may be free.
Typical Q.850 / ISDN cause: 17 (User busy)
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Common causes
- The user is on another call and call waiting is disabled.
- The user pressed reject on their phone (on some devices).
- Channel or concurrent-call limits on a trunk.
How to fix it
- If unexpected, check call-waiting settings and maximum-calls limits on the extension or trunk.
- Carriers sometimes send 486 when the trunk channel count is exhausted. Check your channel limit.
Seeing 486 on calls through a router or firewall? Check that SIP ALG is disabled. It causes a surprising number of SIP errors. Read why.
About 4xx responses
The request has a problem or cannot be completed at this server, usually because of something on the requesting side or the target user.