Choose the trunk object before configuring the PBX
Infobip documents three materially different Infobip trunk types. A static trunk trusts declared public dedicated source IPs and delivers calls to configured customer addresses. A registered trunk uses a PBX or SBC REGISTER exchange with a username and password. A specialized authenticated trunk uses DIGEST credentials and an X-IB-AccessCode header for selected external platforms and supports only TLS connectivity.
Record the ordered type, data centre, signaling target, credential or source-address owner and reset procedure. Administrative, registration and action states describe different parts of the lifecycle: REGISTERED does not prove a number route, available channel or completed call, while an UNREGISTERED state is not applicable to a static trunk.
Documented service facts
Reviewed 2026-09-28. Compare SIP trunk services →
Authentication
DocumentedInfobip documents static trunks authenticated by declared public dedicated source IPs and registered trunks authenticated by username and password. A separate authenticated-trunk type uses DIGEST credentials and an X-IB-AccessCode header for selected external platforms. Record the ordered trunk type and credential owner; these models are not interchangeable.
SIP registration
DocumentedRegistered trunks use a PBX or SBC registration and expose REGISTERED or UNREGISTERED status; static trunks use configured addresses instead. Infobip says disabling a registered trunk forces deregistration. Preserve administrative, registration and action status separately rather than treating one green state as call readiness.
Inbound delivery
DocumentedInfobip documents renting a Voice number, assigning an inbound route and forwarding it through Call Routing to a selected SIP trunk. A static trunk also requires at least one customer destination IP or FQDN. Keep the number, route, destination order and delivered identity distinct from outbound trunk authentication.
Inbound failover
DocumentedStatic trunks can contain multiple customer destination IPs with failover or round-robin selection, while Call Routing can try up to ten destinations in sequence. New FQDN-based trunks in documented paired regions can expose SRV primary and secondary SBC entries; an A lookup returns only the selected data-centre SBC. These paths need separate failure and restoration tests, and none proves survival of established calls.
Number and regional availability
Not verifiedInfobip describes outbound reach across more than 200 countries and self-service SIP acceptance in geographically dispersed data centres, while its Numbers service filters inventory by country and channel capability. Exact number stock, portability, documents, caller-ID rights and activation remain specific to country, number, account and date.
Audio codecs
DocumentedThe trunk reference lists PCMA, PCMU and G.729 plus RFC 2833 and in-band DTMF. A configured option is not proof of end-to-end negotiation, transcoding quality or destination support. Preserve the offer, answer, RTP payloads and DTMF result for every required call path.
T.38 fax
DocumentedInfobip lists T.38 and in-band fax modes and requires fax transcoding choices in trunk configuration. That establishes selectable platform support, not route, carrier, gateway or document success. Qualify the exact number and direction with approved page profiles and retained evidence.
Signaling and media encryption
DocumentedInfobip documents UDP and a TLS/SRTP option for PBX-to-platform signaling and media; its authenticated-trunk type supports only TLS connectivity. Confirm which trunk type, port, certificate-validation behavior, SRTP profile and downgrade policy the account uses. Protection on this leg is not an end-to-end PSTN guarantee.
Concurrent calls and call starts
Not verifiedInfobip defines one channel as one concurrent inbound or outbound call and says the default setup allows up to 1,000 channels per trunk, subject to the ordered plan and account. The reviewed public pages do not establish a calls-per-second or burst limit. Obtain active-call and call-start controls separately before any authorized load test.
Emergency calling
Not verifiedThe reviewed setup page requires a service address for US trunks but describes it as a taxation and regulatory location for the service, not as an emergency-calling activation procedure. No trunk emergency-routing, validated-dispatchable-location, callback or approved test workflow was verified. Confirm these items for every service location before relying on emergency calls.
Pricing model
DocumentedInfobip documents metered and US unlimited channel plans. Metered service combines a channel charge with usage-rated traffic; the US unlimited plan excludes usage charges for domestic outbound traffic subject to fair use, while inbound and other-country traffic remain usage-rated. Capture the current quote, channel quantity, destination rates, numbers, taxes and fair-use terms.
Administration and support
DocumentedInfobip documents portal and API trunk management, separate administrative, registration and action states, credential reset, Call Routing and Voice reports. These controls do not establish an incident SLA or response time. Export trunk, number and route state and retain redacted SIP evidence with the provider case.
SMS
Not verifiedInfobip Numbers can support SMS, MMS or Voice depending on the exact number, and messaging uses separate APIs, sender registration, routing and compliance controls. A voice-capable DID or SIP trunk does not establish SMS enablement. Verify number capability, sender approval, consent, throughput, inbound handling and fees independently.
Bind the number, route and customer destination
Inbound service starts with an Infobip Voice number and its selected inbound action. Call Routing can direct the call to a predefined SIP trunk, while a static trunk requires at least one customer destination IP or FQDN. Preserve the exact number, route filter, ordered destinations, trunk, delivered called-party identity and responsible owner. An outbound call or a successful REGISTER does not validate this chain.
Infobip documents routes with up to ten destinations attempted in sequence. For static trunks, multiple customer destinations can use failover or round-robin selection. Keep response handling, per-destination timeouts, customer-site recovery and established-call behavior as separate evidence; configured alternatives do not establish a completed failover outcome.
Distinguish SBC discovery from customer failover
For accounts receiving a per-trunk FQDN, Infobip documents SRV entries that can expose primary and secondary SBCs in specific paired regions. The A record points only to the selected data-centre SBC, and standalone regions have no paired SRV target. Older accounts can retain static SBC addresses. Record which address model the account actually receives and whether the PBX performs SRV priority and weight processing.
Provider SBC redundancy, customer destination failover, multiple trunks and a Call Routing fallback number solve different failures. Test each approved fault and restoration path with bounded traffic and keep active-call expectations explicit. Do not infer customer-site recovery from the existence of two provider SBCs.
Qualify media, fax and protected transport per route
The trunk reference lists PCMA, PCMU and G.729, plus RFC 2833 and in-band DTMF. It also lists T.38 and in-band fax choices. Preserve the real offer, answer, RTP payloads, DTMF result and fax endpoint for every required direction and destination. A selectable codec or transcoding option is not proof of end-to-end compatibility or document delivery.
Infobip documents UDP and a TLS/SRTP option for the PBX-to-platform leg. Confirm trunk type, port, certificate validation, SRTP profile, keying and downgrade policy, then inspect the negotiated call. Protected transport on this leg is not evidence of encryption beyond the Infobip edge or through the PSTN.
Convert channels and billing language into account facts
Infobip defines one channel as one simultaneous inbound or outbound call and says calls above the trunk's channel allocation are rejected. Its setup page lists a default ceiling of up to 1,000 channels per trunk, but the ordered quantity and account approval govern the real limit. The reviewed public pages do not establish a calls-per-second or burst limit, so obtain call-start controls independently before any authorized load test.
The documentation describes metered and US unlimited channel plans. Metered service combines channel pricing with usage-rated traffic; the US unlimited plan removes usage charges for domestic outbound traffic subject to fair use, while inbound and other-country traffic remain usage-rated. Preserve the current quote, channels, destination rates, number charges, taxes, discounts and fair-use terms rather than converting a plan name into a price.
Keep number capability and emergency service unresolved until verified
Infobip Numbers can support SMS, MMS or Voice depending on the exact number and country. A voice DID or SIP trunk does not establish messaging capability, sender registration, consent, throughput, inbound handling or fees. Portability, documents, inventory and caller-ID rights also remain specific to the number, account and decision date.
The reviewed SIP setup requires a service address for US trunks but describes it as the Place of Primary Use for taxation and regulation. It does not establish an emergency-calling activation, dispatchable-location, callback or approved test workflow. Confirm those items for every operating location before relying on emergency calls. No Infobip account, trunk, registration, number, route, call, codec, fax, encryption, failover, capacity, emergency call, message, price, availability or support response was tested for this guide.
Sources & applicability
Primary references for the technical details above. Operational examples and planning checklists are VoIP.info editorial guidance.
- Infobip SIP trunk types and technical requirements ↗
- Infobip SIP trunk setup ↗
- Infobip Call Routing ↗
- Infobip inbound route selection ↗
- Infobip route execution and troubleshooting ↗
- Infobip Voice number setup ↗
- Infobip Numbers ↗
- Infobip number types ↗
- Infobip SIP Trunks API ↗
- Infobip Voice reports ↗
Examples require adaptation to your topology. No live PBX or hardware testing is claimed.