Freeze one attempt and the exact trunk identity
Record UTC and local time, account and trunk labels, product, authentication mode, SIP address, PBX and version, public and private addresses, transport, called and calling numbers, direction, expected route, answer and audio result. Redact passwords, QR codes, personal data and full call records.
Classify the first unexpected state: portal, registration or IP trust, DNS or proxy, provider attempt, PBX receipt, routing, identity, channel, signaling or media. Do not substitute Hybrid or CrazyPBX instructions for a standard trunk.
Branch on registration or IP authentication
For a register-based trunk, correlate the loaded username and registrar with Live Registrations and Registration Logs. Preserve status, node, expiry, source IP, NAT, socket, contact and the first failed exchange without exposing credentials.
For IP authentication, compare the portal allowlist with the egress public IP and any recent ISP or firewall change. The absence of a registration is expected in this mode; a matching address still does not prove inbound delivery or an accepted outbound identity.
Correlate NAT, DNS, proxy and edge selection
Confirm resolver answers, address family, route, transport and first SIP transaction from the PBX. If a custom outbound proxy is configured, keep the Crazytel SIP address in the server field and the regional hostname only in the outbound-proxy field.
For CGNAT, compare NAT Helper, registration expiry and keepalive to the current provider guidance. A keepalive can preserve a binding but cannot create a static public IP, correct a wrong proxy field or prove both RTP directions.
Prove DID, identity and signaling on one call
For inbound failure, establish whether the expected DID reached the Crazytel edge and then the PBX before changing the dialplan. For outbound failure, preserve the selected trunk, Request-URI, presented identity, Call-ID and response sequence.
Align portal settings, PBX logs, an authorized capture and provider records for the same timestamp. Number ownership, port completion, caller-ID configuration, provider acceptance and remote presentation remain separate evidence.
Separate signaling, codec and media protection
A 200 response or established dialog does not prove audible media. Preserve SDP, negotiated codec, packetization, RTP tuples, packet direction and decoding at authorized points. Crazytel’s G.711a recommendation is not evidence that one call selected it.
On a standard trunk, do not diagnose missing SRTP as an outage when the current provider guide says SRTP is unsupported. On Hybrid or CrazyPBX, verify the exact TLS and SRTP negotiation rather than inferring protection from a TLS socket.
Retest one correction and keep continuity claims separate
After one authorized correction, repeat the affected ordinary call and an unaffected control. Preserve registration or IP trust, provider attempt, PBX receipt, answer, both media directions and hangup. For Divert on Down, record the configured destination, trigger, completed alternate call and restoration separately.
Use the live status page only as a time-stamped service-wide observation, not proof of the account or PBX. Do not place an uncoordinated 000 call; verify address, presented identity, callback and alternate method through Crazytel’s approved process. No trunk, call, media, failover or emergency result was tested for this diagnostic.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
- Crazytel — Creating a Register Based SIP Trunk, updated 26 October 2026 ↗
- Crazytel — CGNAT setup recommendations, updated 26 October 2026 ↗
- Crazytel — SRTP compatibility, updated 26 October 2026 ↗
- Crazytel — Custom outbound proxy settings, updated 26 October 2026 ↗
- Crazytel — No sound on calls, 30 December 2025 ↗
- Crazytel — Real-time network status ↗
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.