---
title: "Set up a SIP trunk to receive and place calls"
description: "Connect your PBX or SBC to Bird in order: create the trunk, deliver incoming calls to your gateways, open outbound calling, and test both directions."
canonical: "https://bird.com/docs/guides/voice/sip-trunk-setup"
---

# Set up a SIP trunk to receive and place calls

This page walks through a complete trunk setup in the order the dashboard needs it. Where skipping a step leaves a visible symptom, the step names it, so you can also use the page as a checklist when a test call fails. For what each setting means, follow the links to [SIP trunks](/docs/guides/voice/sip-trunks), [Receiving calls](/docs/guides/voice/receiving-calls), and [Placing calls](/docs/guides/voice/placing-calls).

## Before you start

- A Bird workspace. Calls, numbers, and trunks belong to one workspace, so do every step in the same one.
- The public addresses of your equipment: the hosts Bird should deliver calls to, and the addresses your equipment sends SIP from.
- For incoming calls, a Bird number in that workspace. For outgoing calls, a caller ID: a Bird number in the workspace or a number you [verified](/docs/guides/voice/caller-ids).
- A Bird number whose `status` is `active`. A number still waiting for its ownership paperwork or its registration carries no incoming or outgoing calls: see [File a number's ownership paperwork](/docs/guides/numbers/ownership-paperwork).

## 1. Create the trunk

Open **Voice** > [**SIP Trunks**](https://bird.com/dashboard/w/voice/sip-trunks), select **Add new SIP trunk**, enter a name, and select **Create trunk**.

A new trunk carries no calls in either direction until you turn each one on.

## 2. Turn on inbound calling

Under **Inbound calling**, select **Enable inbound**. The **Inbound routing** section appears below it.

If you skip this step, numbers cannot be pointed at the trunk: the trunk is missing from the number's trunk list.

## 3. Add your gateways

In **Inbound routing**, open the **Gateways** tab and select **Add gateway** for each address Bird should deliver calls to:

| Field                  | What to enter                                                                             |
| ---------------------- | ----------------------------------------------------------------------------------------- |
| **Name**               | A label you recognize, such as `Primary SBC`                                              |
| **Host**               | The host name or public IP address of your equipment, without `sip:` or a user part       |
| **Port**               | Leave empty for the transport's default port, or enter the port your equipment listens on |
| **Transport**          | UDP, TCP, or TLS, matching your equipment                                                 |
| **R-URI user part**    | How the dialed number is written in the Request-URI. Defaults to E.164 with `+`           |
| **Origination format** | How the calling number is written. Defaults to E.164 with `+`                             |

If your equipment expects numbers without the leading `+`, open the format's list and choose **Without the plus**, or a `00` or `011` international prefix. [What a gateway needs](/docs/guides/voice/receiving-calls#what-a-gateway-needs) explains the number formats.

Your gateway must accept calls from Bird without a SIP Digest challenge, because Bird does not answer one.

## 4. Put the gateways in a group

Bird delivers a call to a group of gateways, so a gateway outside every group never rings. In the **Groups** tab, select **Add group**, name it, and use **Add gateway to group** for each gateway.

For failover, set the group's **Order** to **Weighted** and give the backup gateway a higher **Priority** number. [Deliver calls to a SIP trunk](/docs/guides/voice/receiving-calls#deliver-calls-to-a-sip-trunk) explains each order and the ring time.

When the first gateway is added to a trunk whose routing was never saved, the dashboard creates a group named **All gateways** with that gateway and points the default route at it. Check the group again after you add more gateways.

## 5. Point the default route at the group

In the **Rules** tab, find **Default route** (**No rule above matched**). Set **Then** to **Route to group** and choose your group. Select **Review and save**, then confirm.

The default route answers every call no rule matches, so with no rules it answers every call. If it is set to **Reject**, those calls are refused before they reach your equipment, even with gateways in a group.

In the review, the dashboard warns **Calls never reach some gateways** when a gateway sits in no group that a rule or the default route sends calls to. Fix that warning before you test.

This default route belongs to the trunk. It is separate from the workspace setting **Calls to numbers without their own route** on the **Numbers** page, which decides what happens to numbers that have no route of their own.

## 6. Point your numbers at the trunk

Open **Voice** > [**Numbers**](https://bird.com/dashboard/w/voice/numbers), open the number, and under **Inbound routing** choose **Deliver to a SIP trunk**. Pick the trunk and save.

A number without a route of its own follows the workspace default route, which starts as reject. To send every such number to this trunk at once, set **Calls to numbers without their own route** to the trunk. See [Set a default route](/docs/guides/voice/receiving-calls#set-a-default-route).

If you skip this step while the workspace default route is still reject, incoming calls are rejected and the call record's **Inbound route** shows **Reject the leg**.

## 7. Turn on outbound calling and say who may send

Under **Outbound calling**, select **Enable outbound**. The **Connection** section appears with the trunk's **SIP domain**. Bird identifies your trunk by this domain, so copy it whole.

Then add at least one way to recognize your equipment:

- **Allowed IP addresses**: the public addresses your equipment sends SIP from. Behind NAT, use the router's public address.
- **Allowed API keys**: for equipment that answers a Digest challenge, with username `bird` and an API key secret as the password.

Until outbound is on, the trunk refuses every outgoing call. Until the trunk can recognize your equipment, calls are refused before a call record exists. See [Controlling who may send calls](/docs/guides/voice/sip-trunks#controlling-who-may-send-calls).

## 8. Configure your PBX or SBC

On your PBX or SBC:

- **Send outgoing calls to the trunk's SIP domain.** Put the SIP domain in the Request-URI host. Use port `5060` (UDP or TCP) or `5061` (TLS). A call whose Request-URI host is any other name is refused.
- **Dial in international format.** Put the called number in the Request-URI user part as `+` and the country code, for example `+442071234567`. Do not add a technical prefix. See [What Bird expects on the INVITE](/docs/guides/voice/placing-calls#what-bird-expects-on-the-invite).
- **Present an eligible caller ID** in the `From` header.
- **Offer G.711** (A-law or µ-law) and send DTMF as RFC 4733 telephone events. The same section of that page covers media.
- **Let Bird's calls and audio in.** If your firewall or SBC accepts only listed addresses, it has to accept the calls and audio Bird sends to the gateways you added in step 3.

## 9. Turn on the countries you call

Open **Voice** > [**Destinations**](https://bird.com/dashboard/w/voice/destinations), tick each country you call, and select **Save changes**. A new workspace starts with none enabled, and a call to a disabled country is rejected with `destination_not_enabled`. See [Voice destinations](/docs/guides/voice/destinations).

## 10. Test both directions

1. **Incoming:** call your Bird number from an ordinary phone, then open **Voice** > [**Legs**](https://bird.com/dashboard/w/voice/legs) in the same workspace.
2. **Outgoing:** place a call from your equipment to any reachable number in an enabled country, presenting your Bird number or a verified number as caller ID. You do not need a second Bird number for this.
3. Open each leg. **Inbound route** says what the number was set to do. A rejected call shows its reason and, when the fix is a setting of yours, a link to that setting. A call that worked shows **Answered**. Keep the **Leg ID** if you contact support.

If a call is missing, rejected, or never reaches your equipment, follow [Voice troubleshooting](/docs/guides/voice/troubleshooting), which starts from the symptom.

## Next steps

| Page                                                        | What it covers                                                   |
| ----------------------------------------------------------- | ---------------------------------------------------------------- |
| [SIP trunks](/docs/guides/voice/sip-trunks)                 | Every trunk setting, authentication, and Digest                  |
| [Receiving calls](/docs/guides/voice/receiving-calls)       | Number routes, gateways, groups, and the workspace default route |
| [Placing calls](/docs/guides/voice/placing-calls)           | What Bird expects on the `INVITE`                                |
| [Voice troubleshooting](/docs/guides/voice/troubleshooting) | Diagnosing a call from its symptom                               |

## Related resources

- [What is a voice API?](/explained/voice/what-is-a-voice-api) (answer)
- [Voice](/voice-api) (product)
- [Voice overview](/docs/guides/voice/overview) (docs)

[Get an implementation brief](/learn/workspace?topic=voice)