> ## Documentation Index > Fetch the complete documentation index at: https://www.bolna.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Connect your carrier to Bolna with a SIP trunk > Create a SIP trunk, give your carrier the values Bolna needs, add carrier IPs, gateways and numbers, then confirm the connection with a test call. This guide takes you from nothing to a working trunk: you create the trunk in Bolna, set Bolna's values in your carrier's console, and place a test call in each direction. ## Before you begin Have these from your carrier: * **A SIP trunk with at least one number on it.** Some carriers, Plivo among them, use one trunk for inbound and another for outbound. Create both. * **The gateway host** Bolna dials for outbound calls, for example `acme.pstn.twilio.com`, and its port if it is not `5060`. * **The IP addresses the carrier sends calls from.** Carriers publish these as their signalling IPs. * **A SIP username and password**, only if your carrier issued them for the calls you place. ## Create the trunk In the sidebar, under **Deploy**, open **SIP Trunks** and click **Create trunk**. If your account still has [legacy SIP trunks](/docs/migrating-to-sip-trunks/overview), that page lists them: click **Open new SIP trunks** first. SIP Trunks page in the Bolna dashboard with an empty trunk table and the Create trunk button in the top right The **Provider** step asks *Which carrier is this trunk for?* Pick **Plivo**, **Telnyx**, **Twilio**, **Exotel**, **Vobiz**, **Vonage**, or **Custom** for any other carrier. Then fill in: * **Trunk name**, a label only you see. * **Channels**, the number of simultaneous calls the trunk allows. The default is 10. * **Gateway we dial**, the host Bolna sends outbound calls to. The Telnyx and Exotel presets fill this in. For the others, enter the host your carrier gave your account; the field shows the expected shape. Click **Continue**. Create trunk dialog on the Provider step, with the Plivo carrier tile selected, a trunk name, 10 channels and a Zentrunk domain in the Gateway we dial field The **Carrier IPs** step asks *Which addresses does your carrier call from?* Add every signalling IP or CIDR range your carrier publishes, one at a time. Bolna accepts an inbound call only from these addresses. The Plivo and Exotel presets prefill the addresses those carriers publish, and every preset links to its carrier's IP page. Under **Carrier credentials (optional)**, enter the **Username** and **Password** only if your carrier issued them for the calls Bolna places. Enter both or neither. Click **Continue**. Create trunk dialog on the Carrier IPs step, showing Plivo's prefilled signalling CIDR ranges as removable chips, an address input with an Add button, and empty Username and Password fields under Carrier credentials (optional) The **Numbers** step asks *Which numbers arrive on this trunk?* Enter each number in E.164 format, starting with `+`, and click **Add**. This step is optional; you can add numbers later. Click **Continue**. Create trunk dialog on the Numbers step, with one E.164 number added and its destination key shown underneath The **Review** step summarizes the trunk and shows the first thing to do in your carrier's console for each direction. Click **Create trunk**. The trunk page opens, and its health reads **Waiting for carrier** until the first call crosses it. Create trunk dialog on the Review step, summarizing provider, carrier IPs, carrier credentials, gateways and numbers, with Inbound and Outbound next-step cards and a Create trunk button ## Set Bolna's values at your carrier Open the trunk's **Overview** tab. Under **Carrier setup**, the **Inbound, carrier to Bolna** and **Outbound, Bolna to carrier** cards list every value your carrier needs, each with a copy button. Expand the steps under each card, for example **Plivo inbound trunk steps**, for a checklist written for your carrier's console. Trunk Overview tab with a Waiting for carrier health badge, and the Carrier setup section showing the Inbound, carrier to Bolna card and the Outbound, Bolna to carrier card with copy buttons ### Inbound: carrier to Bolna Set these on your carrier's origination (inbound) trunk: | Setting | Value | | - | - | | Origination URI | `sip:trunk.bolna.ai:5060` for UDP, or `sip:trunk.bolna.ai:5060;transport=tcp` for TCP | | If the carrier accepts only an IP | `15.252.21.46`, port `5060` | | Number format | E.164, with or without the `+` | | Codecs | `PCMU` and `PCMA`. Turn off any others, such as G.729. | | DTMF | RFC 2833 | Your carrier must send each INVITE with an SDP offer, from an address on the trunk's carrier IPs. Assign your numbers to this origination trunk in the carrier's console. ### Outbound: Bolna to carrier Set these on your carrier's termination (outbound) trunk: | Setting | Value | | - | - | | IP allowlist (signalling) | `15.252.21.46` and `13.206.230.198` | | Media (RTP), both directions | UDP `30000`-`40000`, to and from `15.252.21.46` | | Credentials | Optional. If you use a credential list instead of, or as well as, the IP allowlist, enter the same username and password on the trunk in Bolna. | | Caller ID | One of your trunk numbers, in E.164 with the `+` | | Codecs | `PCMU` and `PCMA` | Allowlist both Bolna IPs. `13.206.230.198` is reserved for a second edge, so listing it now means no carrier change later. ## Manage carrier IPs, gateways and credentials The trunk's **Connection** tab holds both directions. Changes take effect on live traffic. Trunk Connection tab with the Inbound: carrier IPs list on the left, the Outbound: gateways list with a Dial with leading plus switch and Carrier credentials row on the right, and the Advanced row below showing UDP, PCMU, PCMA and RFC 2833 DTMF **Inbound: carrier IPs.** Click **Add IP** to add an address or CIDR range. Changes apply within 5 seconds. Each entry must be a public IPv4 address or range, no broader than `/16`, and a trunk holds up to 32. With no carrier IPs, every inbound call is refused. **Outbound: gateways.** Click **Add gateway** and enter the **Host**, **Port** and **Priority**. A trunk holds up to 8 gateways, tried in priority order, lowest first. The host must be a public IPv4 address or a DNS name. If a gateway times out, answers `408` or `478`, or answers with a `5xx`, Bolna tries the next gateway. Any other answer, such as busy, a decline or no answer within 60 seconds, ends the call. * **Dial with leading plus** sends the number you call as `+`. Off, the default, sends the digits alone. Pick whichever your carrier expects. * **Carrier credentials** holds the username and password Bolna sends when your carrier challenges an outbound call with `401` or `407`. The password is stored encrypted and never shown again. **Advanced.** Click **Edit** to change the **Transport** (UDP or TCP) Bolna uses to reach your gateways, the **Channels**, and the **Codecs** (`PCMU`, `PCMA`, or both). DTMF is always RFC 2833. If another trunk on Bolna dials the same gateway host or address, both trunks must have carrier credentials. Without them, the carrier cannot tell the trunks apart by Bolna's shared IPs, so Bolna refuses the gateway with `409 gateway_conflict`. ## Add numbers Open the **Numbers** tab and click **Add number**. * **Number** is the number in E.164 format, starting with `+`. * **Destination key** is the called number exactly as your carrier puts it in the Request-URI. Leave it blank to use the number's digits without the `+`. Set it when your carrier sends something else, such as a national format. An inbound call matches a number when the called number equals the E.164 number, with or without the `+`, or equals the destination key. A number can be on only one trunk at a time; adding one that is already on a trunk fails with `409 number_taken`. Add number dialog with a Number field holding an E.164 number and a Destination key field showing the digits as a placeholder Next, [assign an agent to each number](/docs/sip-trunking/inbound-calls) so inbound calls are answered. ## Verify with a test call The trunk tests itself without an agent. Open the **Activity** tab, or click **Test trunk** at the top of the trunk page. Under **Test inbound**, click **Start listening**, then dial the number shown from any phone within five minutes. Bolna answers and plays your voice back to you about a second later. While the trunk is listening, the next call to any of its numbers reaches the test instead of your agent. **Stop listening** cancels the test before a call arrives. Under **Test outbound**, enter a phone number you can answer and click **Place echo call**. Bolna calls it from the trunk's first number, through its gateways in priority order. Answer, speak, and you hear yourself about a second later. The call ends after a minute. Each test shows its state, ending in **Completed** or **Failed**. A failed test shows the SIP code and cause the carrier returned. See [Troubleshooting](/docs/sip-trunking/troubleshooting) for what each one means. Trunk Activity tab with the Test inbound card waiting for a call, showing Dial the number now, Listening for a countdown and a Stop listening button, and the Test outbound card with a number in the Number to call field next to the Place echo call button A trunk runs one test at a time and allows five tests every ten minutes. A test uses one of the trunk's channels while it runs. Tests do not appear in Call History or under **Recent calls**, and they do not change the trunk's health, which stays **Waiting for carrier** until a real call crosses the trunk. ## Using the API Every step above has an API equivalent. Send your API key as a Bearer token; see [Authentication](/docs/api-reference/authentication). These requests use the [create trunk](/docs/api-reference/trunks/create), [add carrier IP](/docs/api-reference/trunks/add_carrier_ip), [add gateway](/docs/api-reference/trunks/add_gateway), [update trunk](/docs/api-reference/trunks/update), [add number](/docs/api-reference/trunks/add_number) and [connection details](/docs/api-reference/trunks/connection_details) endpoints. ```bash Create a trunk theme={"system"} curl -X POST https://api.bolna.ai/trunk/trunks \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "name": "Acme India", "preset": "plivo", "channels": 10, "transport": "udp", "codecs": "PCMU,PCMA", "outbound_leading_plus_enabled": false, "gateways": [ { "host": "21784177241578.zt.plivo.com", "port": 5060, "priority": 1 } ], "ip_acls": ["15.207.90.192/31", "204.89.151.128/27"], "auth_username": "", "auth_password": "" }' ``` ```bash Add a carrier IP theme={"system"} curl -X POST https://api.bolna.ai/trunk/trunks//ip-acls \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "cidr": "13.52.9.0/25" }' ``` ```bash Add a gateway theme={"system"} curl -X POST https://api.bolna.ai/trunk/trunks//gateways \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "host": "sip-backup.example.com", "port": 5060, "priority": 2 }' ``` ```bash Set credentials and transport theme={"system"} curl -X PATCH https://api.bolna.ai/trunk/trunks/ \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "auth_username": "", "auth_password": "", "transport": "tcp" }' ``` ```bash Add a number theme={"system"} curl -X POST https://api.bolna.ai/trunk/trunks//numbers \ -H "Authorization: Bearer " \ -H "Content-Type: application/json" \ -d '{ "e164": "+918045678901", "destination_key": "918045678901" }' ``` ```bash Get Bolna's values theme={"system"} curl https://api.bolna.ai/trunk/pop \ -H "Authorization: Bearer " ``` `GET /trunk/pop` returns the values to give your carrier: ```json theme={"system"} { "sip_domain": "trunk.bolna.ai", "ips": ["15.252.21.46", "13.206.230.198"], "port": 5060, "transports": ["udp", "tcp"], "rtp_ports": "30000-40000" } ``` A few rules the API enforces: * `preset` records which carrier template the trunk came from. The API does not fill any values from it; send the gateways, transport and carrier IPs yourself. * `transport` is `udp` (the default) or `tcp`. * `codecs` is `PCMU`, `PCMA`, or both, comma-separated. * `auth_username` and `auth_password` are set together and cleared together. To clear them, send both as `null`. * `destination_key` is required when adding a number through the API. Send the number's digits without the `+` unless your carrier sends something else. * `gateway.priority` is 0 to 100, lowest tried first. The trunk's `health` field reads `waiting_for_carrier` until the first call, `ready` after it, `degraded` after three outbound calls in a row fail at the carrier (an answered call resets this), and `disabled` while `is_active` is `false`. ## Next steps Assign an agent to each number. Switch an agent to the trunk and place calls. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.