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A saved hostname proves only that an endpoint was entered. It does not prove direction, authentication, source addresses, or a successful inbound call. Keep the exact DID, route it to the platform SIP FQDN, and obtain current provider-to-destination authentication details. If no stable list is published, ask support for the account’s complete SIP-signaling source CIDRs and failover regions. Never use media ranges or another customer’s addresses. Running your own PBX or contact-center platform — 3CX, Asterisk/FreePBX, Starface, Genesys Cloud, Five9, or Aircall? See PBX & contact center platforms for step-by-step setup, codec settings, and the failure modes specific to each.
If a provider doesn’t support a static SIP trunk at all, you don’t have to give up on the number. Forward it to a number purchased through the platform for inbound calls, and place outbound calls from that platform number instead.
Status: sip.1und1.de is normally a registrar/termination host, not evidence of external FQDN forwarding. No verified global source list is included. Action: confirm product support, sent DID format, and all signaling sources with 1&1.
Status: supported, with a dedicated setup that splits outbound (a Fonial SIP user) from inbound (SIP-URI forwarding), and requires Fonial’s paid PLUS plan. See the Fonial guide for the full walkthrough.
Status: a localphone.com endpoint alone is not a verified inbound profile. Action: confirm external SIP-URI routing, DID format, transport, and signaling sources with Localphone.
Status: the hostname can identify a PBX or reseller; no global list is verified. Action: identify the actual operator and obtain account-specific public signaling addresses.
Status: routing a DID to a SIP URI is supported, but auth and sources follow current account/trunk documentation. DIDWW uses two separate trunks — inbound routes to the platform SIP FQDN, and outbound authenticates against out.didww.com. Action: use current DIDWW sources; never reuse DIDLogic addresses. Send outbound numbers in E.164 without the leading + — DIDWW expects that exact format, and it’s an easy detail to miss.
See the Zadarma guide for API keys, automatic import, manual direct SIP and PBX forwarding. Use the signaling list for the selected path.
Status: capabilities vary by product and region. sipcall’s default trunk type registers (Endgerät); the platform needs the non-registering, static Anlagenanschluss mode instead — not the option a new sipcall customer would normally pick. Action: ask support for external SIP-URI routing, number format, transport, and current sources. Use Digest authentication, and set codecs to G.711 a-law with Opus and G.722 disabled (the Swiss default). If outbound calls get a 403, check that the caller ID is verified on the account.
Status: generic SIP/BYOC depends on the purchased product. RingCentral has no wholesale SIP trunk for retail accounts; connect by provisioning a Generic SIP IP Phone instead, which requires MVP/RingEX Standard or higher — entry plans don’t expose it. Action: confirm external SIP destination support and request current regional signaling ranges. Always point at the global sip.ringcentral.com host, never a regional sipXX.ringcentral.com address (those are reserved for RingCentral’s own desk phones). A newly created SIP endpoint needs one to two minutes to propagate through RingCentral’s anti-flood protection — testing immediately produces spurious 403/404 errors, and retrying during that window can extend the lockout.
Status: Voice Connectors use region-specific signaling information. Chime’s Voice Connector defaults to Encryption: Enabled, which requires TLS and SRTP — if the platform side of the trunk falls back to plain UDP on port 5060, the call fails with no media and no obvious error. Action: use the current data for the selected AWS region; never reuse another region’s addresses. The outbound host follows <voice-connector-id>.voiceconnector.chime.aws. Chime also gates outbound by Calling Plan — a destination country not explicitly enabled on the AWS account is blocked, independent of any platform-side dialing permissions.
Status: no verified direct external-FQDN profile is documented here. Action: treat it as unsupported until Placetel confirms route, number format, auth, transport, and source ranges in writing. No static trunk? Use the fallback above.
Status: capabilities and SBC addresses vary by country/product. Action: request the exact external SIP route and regional source networks for the account. No static trunk? Use the fallback above.
Status: Cloud PBX interconnect is product-controlled; no global list is asserted. Action: use a support-assisted setup and only the destination/source networks supplied by NFON. No static trunk? Use the fallback above.
Status: trunking and forwarding are product-specific; no global list is asserted. Action: confirm external SIP-URI routing and current signaling sources before saving. No static trunk? Use the fallback above.
Status: no current provider-to-platform authentication profile is documented here. Action: identify the exact product and region, then obtain the current FQDN-routing method and complete signaling sources from the provider or account portal.
Status: a saved hostname or credential mode is not proof of downstream Digest support. Action: confirm the account’s external SIP destination support, DID format, transport, and current public signaling sources.

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Required confirmation

Ask whether the DID can be delivered to an external FQDN without REGISTER; the exact DID format in the Request-URI; whether the provider authenticates toward the destination with Digest and where those origination credentials are set; otherwise all signaling CIDRs and failover regions; TCP 5060 or TLS 5061; and whether SRTP is required. Only an external call with a platform inbound record, the assigned assistant, and two-way audio confirms the integration. Reject allowlist entries that contain prose, placeholders, hostnames, or unrelated public resolvers such as 8.8.8.8. A provider network written without its CIDR prefix is only one host and must not be silently expanded or corrected. Sources: DIDWW, Fonial, Amazon Chime, Zadarma, sipcall, RingCentral, Placetel, Peoplefone, NFON, Sipgate. Accessed 22 August 2026.