SIP trunking

Import your Zernio numbers into ElevenLabs, Retell, Vapi, LiveKit or your own PBX.

Get a number Request SIP access

Inbound + outbound
TLS + SRTP by default
No per-channel fees

Incoming call

+1 646 555 0199 to +1 415 555 0123

INVITE +14155550123

ElevenLabs production

SIP trunk · 3 numbers attached

Deliver tosip.rtc.elevenlabs.io:5061

Outbound viasip.telnyx.com

Usernamezernio3f9a1c7b2e04

TLS · SRTP

Support agent answered

On your platform · 00:14

Encrypted

Join 70,000+ of the world's most ambitious developers and builders

How It Works

From number to agent in three steps

Early access, switched on per workspace on request.

New SIP trunk

Platform

ElevenLabs

Deliver inbound calls to

sip.rtc.elevenlabs.io:5061

TLSTCPUDP

Create trunk

Create a trunk

Pick a platform preset or enter any SIP hostname.

Trunk created

Copy the password now. It is not shown again.

SIP server

sip.telnyx.com

Username

zernio3f9a1c7b2e04

Password

8d1e••••••••••••••••c07a

Paste the credentials

Your agent can now call out as your number.

Attach a number

Its inbound calls go to this trunk.

+1 415 555 0123

+1 312 555 0187

+44 7700 900412

Attach

Attach a number

Its inbound calls ring your agent directly.

Number search

Start with a number

Trunks carry numbers bought on Zernio, so start with one.

The hidden digits show once you sign up. Calls included on every number.

Already have a number? Check if you can move it

Setup

What goes where, per platform

Zernio needs your platform's SIP host. Your platform needs the trunk's credentials.

In Zernio

Where inbound calls are delivered.

SIP hostsip.rtc.elevenlabs.io

TransportTLS on 5061

In ElevenLabs

How your agent places calls from your number.

SIP serversip.telnyx.com

Usernamezernio3f9a1c7b2e04

PasswordShown once, when the trunk is created

Phone number+14155550123

Dashboard preset, tested live with transfers.

TLS and SRTP by default

TLS on 5061 with encrypted media. TCP or UDP on 5060 if your side needs it.

Numbers arrive in E.164

Both numbers arrive in +E.164, the exact form ElevenLabs and Retell match on.

Transfers work mid-call

SIP REFER works, so your agent can hand a caller to a person.

One trunk per client

Up to 10 trunks, each with its own credentials and spend cap.

Rotate credentials in one call

One API call issues a new password and retires the old one.

Texts stay on Zernio

Only voice moves. SMS and WhatsApp messages stay on the Zernio API.

Trunk or forward

Two ways to reach your agent

Choose per number, based on who should own the call.

SIP trunk

Your platform owns the call both ways, recordings included.

Create a trunk

Call forwarding

Zernio answers and bridges to sip:, tel: or wss://, with IVR and call history.

See the Voice API

Both, number by number

Trunk your agent lines, forward your support line.

API

Two calls to a live trunk

Rotate, detach and delete are one call each too.

POST /v1/phone-numbers/sip-trunks

curl -X POST https://zernio.com/api/v1/phone-numbers/sip-trunks \
  -H "Authorization: Bearer $ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"label":"ElevenLabs production","sipHost":"sip.rtc.elevenlabs.io"}'

{
  "id": "66f1c2b3d4e5f6a7b8c9d0e1",
  "sipHost": "sip.rtc.elevenlabs.io",
  "sipPort": 5061,
  "transport": "tls",
  "termination": { "uri": "sip.telnyx.com", "username": "zernio3f9a1c7b2e04" },
  "digestPassword": "8d1e…c07a"  // shown only here
}

curl -X POST https://zernio.com/api/v1/phone-numbers/NUMBER_ID/sip-trunk \
  -H "Authorization: Bearer $ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"trunkId":"66f1c2b3d4e5f6a7b8c9d0e1"}'

Limits

Every trunk cap, written down

Enforced by the carrier on every trunk, so a leaked password has a ceiling.

Read the docs

10 callsConcurrent calls per trunk. Add a trunk to run more.

$25 / dayOutbound spend per trunk, enforced by the carrier.

$0.30 / minThe most expensive destination a trunk will dial.

57 countriesOutbound reaches the countries we sell numbers in.

10 trunksPer workspace. Several can share one host.

HostnameCalls are delivered to a DNS name, never a raw IP.

60 s minimumAn outbound call under a minute bills as a full minute.

Pricing

No trunk fee, no channel fee

You pay for the number and its minutes, priced by destination.

See pricing

Numbers from

per month

SIP trunk

No fee

Channels

No per-channel fee

Minutes

Per call, by destination

Frequently Asked Questions

Put your agent on a real phone number

Buy a number, request access, take the first call on your platform.

Start for free Read the docs

Inbound + outbound
TLS + SRTP by default
No per-channel fees