When it happens
- A wrong or unallocated number.
What to check
- Check the number.
What the response looks like
SIP/2.0 604 Does Not Exist Anywhere
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK776asdhds
From: <sip:101@pbx.example>;tag=1928301774
To: <sip:+15551234567@pbx.example>;tag=a6c85cf
Call-ID: a84b4c76e66710@203.0.113.10
CSeq: 2 INVITE
Reason: Q.850;cause=1;text="Unallocated (unassigned) number"
Content-Length: 0