# 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](outbound-dialing.html#outbound-dialing-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](https://datatracker.ietf.org/doc/html/rfc5806), 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](../../../phone-numbers/buy-numbers/how-to-buy.html#user-panel-purchase).
- An active outbound trunk. [Create an outbound trunk](../how-to-guides/create-outbound-trunk.html#outbound-trunk-create-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](mailto:support%40didww.com).

### 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]](#id9) | Greece | Iceland | Ireland | Israel |
| Italy [[2]](#id11) | Lithuania | Luxembourg | Malta | Mexico |
| Netherlands | New Zealand | Nigeria | Norway | Panama |
| Peru | Poland [[2]](#id11) | Portugal [[3]](#id12) | Puerto Rico | Serbia |
| Slovakia | South Africa | Spain | Sweden [[1]](#id9) | Switzerland [[1]](#id9) |
| Thailand [[1]](#id9) | United Kingdom | United States |  |  |

[1]
([1](#id2),[2](#id6),[3](#id7),[4](#id8))

Additional prerequisites apply for Germany, Sweden, Switzerland, and
Thailand. Contact [DIDWW Customer Support](mailto:support%40didww.com) for details.


[2]
([1](#id3),[2](#id4))

Only local DID numbers are supported.


[[3](#id5)]

Only National DID group **351-30** supports diversion.

## Related resources

- [Outbound dialing](outbound-dialing.html) - Understand local route requirements and
  destination formatting.
- [Caller ID and CNAM OUT](../caller-id-cnam-out.html) - Configure Caller ID formatting and CNAM
  behavior.
- [Outbound SIP information](../outbound-sip-information.html) - Find SIP endpoints and transport
  details.

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