604 6xx Global failure RFC 3261
SIP 604 Does Not Exist Anywhere
The server has authoritative information that the user does not exist anywhere.
Typical Q.850 / ISDN cause: 1 (Unallocated (unassigned) number)
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Common causes
- Invalid or unallocated number.
How to fix it
- Verify the number. Remove it from dialling lists.
Seeing 604 on calls through a router or firewall? Check that SIP ALG is disabled. It causes a surprising number of SIP errors. Read why.
About 6xx responses
The request cannot succeed anywhere. The caller should not retry it elsewhere.