Call forwarding#

Automatically redirect incoming calls from your DID number to another destination using local in-country routing. Forwarded calls are delivered through your configured outbound trunk, with diversion routing enabled to preserve the original caller and DID information, ensuring callers can still reach you even when your primary device or platform is unavailable.

Concrete telephone numbers in this page use the NANPA range reserved for fictional use.

Call forwarding through this service is supported only for local routes.

How diversion routing works#

Diversion routing is a SIP-based mechanism used to redirect inbound calls to another destination by including the SIP Diversion header in the signaling. The PBX or SBC includes this header, defined in RFC 5806, when it forwards the call. The header carries the originally called DID and diversion reason. DIDWW validates that the DID belongs to the account and uses the corresponding local route.

Requirements#

  • Equipment that supports the SIP Diversion header.

  • A DID with the Local CLI feature, available through How to buy numbers.

  • An active outbound trunk. Create an outbound trunk if you do not have one yet.

  • Diversion service enabled on the outbound trunk.

Important

To enable diversion routing on your outbound trunk, request activation of the diversion service by contacting DIDWW Customer Support.

Call flow#

  1. An inbound call arrives on the DID.

  2. DIDWW sends the inbound call to the PBX or SBC.

  3. When forwarding the call, the PBX or SBC sends it through a diversion-enabled outbound trunk and adds or preserves a Diversion header containing the originally called DID. For example:

    Diversion: <sip:+12025550199@sip.didww.com>;reason=unconditional

  4. DIDWW validates that the DID in the header belongs to the account.

  5. DIDWW routes the call through the local in-country termination partner.

Note

Forwarded calls should be sent only through an outbound trunk with the diversion service enabled.

Call Flow Diagram
        sequenceDiagram
    autonumber
    participant C as Caller
    participant DIn as DIDWW inbound trunk
    participant PBX as PBX or SBC
    participant DOut as DIDWW outbound trunk
    participant P as PSTN destination

    C->>DIn: INVITE to DID (+12025550199)
    DIn->>PBX: Deliver inbound call
    PBX->>DOut: INVITE to forwarded number with Diversion header
    DOut->>DOut: Validate DID in Diversion header
    DOut->>P: Route call
    P-->>DOut: 200 OK
    DOut-->>PBX: 200 OK
    PBX-->>DIn: 200 OK
    DIn-->>C: 200 OK
    Note over C,P: Call connected and media follows the negotiated path
Use Cases

  • Unconditional Forwarding (CFU) – Forward all calls immediately to another destination (e.g., voicemail or mobile), preserving the original DID and diversion reason.

  • Call Forward on Busy (CFB) – Redirect callers to another endpoint when the primary device is busy.

  • Call Forward on No-Answer (CFNA) – Divert calls after a timeout period while keeping the original caller ID and DID.

  • Call Forward on Unavailable (CFUNV) – Route calls to backup numbers when the endpoint is offline or unreachable.

  • Automatic Call Distribution (ACD) – Divert calls to queues or after-hours destinations while retaining the full diversion chain.

  • Voicemail – Deliver calls to voicemail systems with the correct diversion reason and original called number.

  • Call Tracking – Preserve campaign/source identifiers by maintaining the original DID in the Diversion header.

Supported countries for diversion routing#

Argentina

Australia

Austria

Belgium

Bosnia and Herzegovina

Brazil

Bulgaria

Canada

Czech Republic

Chile

Croatia

Denmark

Finland

France

Georgia

Germany [1]

Greece

Iceland

Ireland

Israel

Italy [2]

Lithuania

Luxembourg

Malta

Mexico

Netherlands

New Zealand

Nigeria

Norway

Panama

Peru

Poland [2]

Portugal [3]

Puerto Rico

Serbia

Slovakia

South Africa

Spain

Sweden [1]

Switzerland [1]

Thailand [1]

United Kingdom

United States