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What is a SIP trunk used for in a Bolna voice agent?
A SIP trunk connects the carrier you already use to Bolna, so your voice agents answer calls on your own numbers and place calls from them while your carrier bills the minutes. Your carrier sends inbound calls to Bolna's SIP edge at trunk.bolna.ai, and Bolna sends outbound calls to your carrier's gateway with one of your trunk numbers as the caller ID. Legacy SIP trunks keep working, but new trunks use this setup.
How do I connect my SIP trunk to Bolna?
- Get from your carrier: a SIP trunk with at least one number, the gateway host Bolna dials, the IPs the carrier sends calls from, and a SIP username and password if it issued them.
- In the Bolna dashboard, under Deploy, open SIP Trunks and click Create trunk. Pick Plivo, Telnyx, Twilio, Exotel, Vobiz, Vonage or Custom, and enter a trunk name, channels and Gateway we dial.
- On the Carrier IPs step, add every signalling IP or CIDR range your carrier publishes. Add carrier credentials only if your carrier issued them.
- Add your numbers in E.164 format and click Create trunk.
- At your carrier, set the origination URI to
sip:trunk.bolna.ai:5060(orsip:trunk.bolna.ai:5060;transport=tcp), and allowlist15.252.21.46and13.206.230.198on the termination trunk. - Use Test trunk to place an echo call in each direction. Then assign an agent to each number, and set an agent's Telephony Provider to SIP Trunk to call out.
The full walkthrough is in the connect your carrier guide in the Bolna docs. For how calls flow, see the SIP trunk overview.
Which SIP settings does Bolna support?
| Setting | What Bolna supports |
|---|---|
| Inbound address | sip:trunk.bolna.ai:5060, or 15.252.21.46 port 5060 if the carrier accepts only an IP |
| Transport | UDP (default) or TCP on port 5060 |
| Bolna IPs to allowlist | 15.252.21.46 and 13.206.230.198 |
| Audio (RTP) | UDP 30000 to 40000, to and from 15.252.21.46 |
| Codecs | PCMU and PCMA only |
| DTMF | RFC 2833 telephone events |
| Outbound authentication | Bolna's IPs, carrier credentials sent on a 401 or 407 challenge, or both |
| Channels per trunk | 1 to 1,000, default 10 |
| Gateways per trunk | Up to 8, tried in priority order |
| Carrier IPs per trunk | Up to 32 public IPv4 addresses or ranges, each /16 or narrower |
| Inbound headers to the agent | P-Asserted-Identity, Diversion, Call-ID and up to 20 custom X- headers |
Which carriers have a SIP trunk guide for Bolna?
| Carrier | Create the trunk with | Indian numbers | Guide |
|---|---|---|---|
| Acefone | Custom | Yes | Acefone SIP trunking |
| Airtel | Custom | Yes | Airtel SIP trunking |
| Exotel | Exotel preset | Yes | Exotel SIP |
| Plivo | Plivo preset | Yes, with a Plivo account in its India data region | Plivo SIP trunking |
| Telnyx | Telnyx preset | Telnyx SIP trunking | |
| Twilio | Twilio preset | Twilio SIP trunking | |
| Vobiz | Vobiz preset | Yes | Vobiz SIP trunking |
| VoiceLink | Custom | Yes | VoiceLink SIP trunking |
| Vonage | Vonage preset | Vonage SIP trunking |
For calls on Indian numbers, enter them in E.164 format such as +91XXXXXXXXXX. Commercial and telemarketing calls in India need DLT-registered 140-series or 160-series numbers. The carrier guides in the Bolna docs list the preset for each carrier.
What can you build with your own SIP trunk and Bolna?
Keep your carrier and numbers. Your numbers stay with your carrier. You point them at Bolna instead of porting them, and each number can be on one trunk at a time.
Control call costs. Calls run on your carrier's minutes and rates. See pricing for what Bolna charges for the AI side.
Gateway failover. If a gateway times out or answers 408, 478 or a 5xx, Bolna tries the next one in priority order.
Carrier data in the conversation. Map inbound SIP headers to prompt variables, or use one as the lookup key for caller data.
Follow a carrier guide. See Twilio, Plivo, Vobiz, Exotel, Airtel, Acefone and VoiceLink.