485 4xx Client error RFC 3261
SIP 485 Ambiguous
The Request-URI matched more than one user and the server could not choose.
Typical Q.850 / ISDN cause: 1 (Unallocated (unassigned) number)
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Common causes
- Overlapping user names or dial patterns.
How to fix it
- Make the dialled address or dialplan patterns unique.
Seeing 485 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.