How it works
This response may occur when the server cannot match a requested SIP URI to an address or routing entry. It describes the result of a specific request, not necessarily the health of the whole network. The responding node is important when diagnosing the cause.
Business example
A technician sees SIP 404 when calling an extension and reviews the dial plan, addressed domain and destination registration.
What to consider
Identify which server generated the response before changing routing rules. An incorrect URI and a missing dial-plan entry can produce similar symptoms.