Connecting a client PBX or gateway (SIP trunk)

What is a SIP trunk?

SIP trunking is a way for businesses to connect their phone system to the public switched telephone network (PSTN) using the internet instead of traditional phone lines. It uses SIP protocol to transmit voice traffic between your software and external numbers.

With SIP trunking, you don’t need physical equipment - calls are handled through a virtual connection, over the internet. You can use SIP trunk to merge multiple offices or remote teams into a single communication system, centrally managing their operations and adjusting system settings when needed. Flexibility of VoIP solutions is what traditional telephony cannot match.

Who needs SIP trunk

Small business

Telecom professionals and integrators

Companies expanding global presence

If you're setting up business telephony for the first time, our platform is designed to make it simple. You’ll find clear instructions, and 24/7 support to help at every step. Whether you're an IT admin or a complete novice, you can get your system up and running in a couple of minutes. Connect an in-house PBX via SIP trunk, or create a Cloud PBX in Zadarma and use it directly, without a trunk.

Cloud PBX unlocks you powerful features - integrations with CRM and AI services, and more - all in one place.

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If you have already had experience with VoIP, our platform gives you the tools to take the next step. Connect your PBX via IP authorization or login-password, and enjoy virtual numbers as well as low call rates from a reliable telephony provider without changing your setup. Zadarma is a complete ecosystem for those ready to explore more advanced communication solutions.

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For companies expanding into international markets, we make it easy to grow beyond boundaries. Get local phone numbers in 110 countries, use cost-effective local and international trunks, and keep your team and customers connected - no matter where they are.

You can also connect an existing PBX system to our SIP trunk to extend its possibilities without changing the current setup.

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Zadarma SIP trunk Advantages

Flexible setup

All configuration is handled online and can be adjusted at any time. Change setup easily to match the business needs - from simple scenarios to complex infrastructure.

Global access

Make and receive calls from any part of the world using a computer, phone or even a browser. No additional equipment required.

Uninterrupted service

Zadarma has 6 data centers on three continents, ensuring trouble-free operation. Our SLA guarantees 99,9% uptime for all users regardless of the price plan.

High security standards

Zadarma has successfully passed ISO/IEC 27001 certification, confirming its infrastructure and work processes align with world’s best-known standards.

Transparent pricing

Choose between pay-as-you-go plans or bundles. Pricing is clear, predictable, and tailored to different call volumes.

Best call quality

We only acquire premium quality services from the world's largest VoIP providers, which offer good sound clarity and guarantee CallerID transmission.

Extensive Number Coverage

Access virtual numbers in 110 countries to establish local presence wherever you operate.

Future-proof system

We keep the bar high and deploy new features regularly, so you can access the most up-to-date tools. Among the first, we present integrations with CRMs and AI platforms.

24/7 Customer Support

Available in 8 languages via chat, a ticket system and phone.

Zadarma IP telephony meets the requirements of globally active entrepreneurs, because they can organize their company from anywhere in the world and connect all their employees in one network with customers and partners.

Zadarma understands how integral communication and building relationships are to businesses at every stage.

Zadarma’s VoIP services help you separate work from personal at an incredible price

Zadarma's tech team is always looking to evolve their cloud-based business phone software (PBX) to accommodate the ever-changing new normal global communication needs. There are many advantages to Zadarma's VoIP solution.

European telecom provider Zadarma has successfully integrated three of the leading AI-powered voice assistants into its cloud telephony and virtual PBX platform.

By choosing Zadarma, you get a variety of flexible tools that help your business stay competitive and connected.

Zadarma focuses on offering reliable cloud communication services for businesses and individuals around the world.

Zadarma is a globally recognised PBX vendor, offering a popular cloud PBX phone system. This ready to go, affordable phone system is simple to set up and comes with a variety of call management features, creating a versatile business phone system for growing businesses.

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How to connect SIP trunk in 3 simple steps

Create an account

To start using our services, register on our website.

Order a virtual number

In the personal area, select a number you want to connect and fill in the information on the order page. The number will be connected after the verification of provided details. This process can take up to 1 working day, in the meantime you can set up software or hardware.

Configure equipment

You can connect any app or equipment that works via SIP to Zadarma. There are two ways of connection:

Option 1

Using the SIP login and password

The easiest and the fastest method that is supported by all equipment types.

To connect, simply register and copy the connection data from the Settings - SIP Connection tab. You can find the setup instructions for popular hardware equipment and software settings on the website.

The connection is suitable for small and large systems. However, there is a drawback: CallerID (a purchased number used for outgoing calls) can be changed only from the personal area.

Option 2

Creating the SIP trunk with IP authorization

Suitable for large call centers and VoIP providers. Enables the transfer of any amount of connected numbers as a CallerID.

A fixed external IP address is mandatory for this type of connection. You can find more information about IP authorization setup in the "FAQ" section. After enabling this type of connection, your SIP login will no longer receive incoming calls. They should be forwarded via SIP URI to your server or received on a free SIP login.

If you don’t have a phone system yet and want to create it from scratch, follow this guide for Zadarma cloud PBX.

Main Features

P-Asserted-Identity (PAI) Header Support

Transmit a specific CallerID from the list of connected numbers when making calls from your server.

Call routing to SIP URI

Forward incoming calls to any SIP address. Ideal for working with PBXs hosted on external servers or AI voice tools.

TLS and SRTP encryption

Secure your SIP signaling and voice streams with modern encryption standards. Recommended for any business handling sensitive data across public networks.

Different SIP trunk connection types

Choose between IP authorization or login-password authentication when connecting your equipment. The first method requires fixed external IP, while the second one can be used both with fixed and dynamic IP.

Restriction by IP

Secure your phone system by enabling IP restriction for outgoing calls. It only takes a few clicks, but ensures only authorized devices will be able to make calls.

API and Webhook interface

Build custom integrations, receive real-time information, or connect telephony to your internal systems. API is completely free and available for all users.

Direct routing for Microsoft Teams

Zadarma SIP trunk connects to MS Teams through direct routing, allowing users to make and receive calls without leaving Teams. This integration is a practical way to merge internal and external communication in one place, empowering Teams functionality with Zadarma features.

Call Tracking with Google Analytics

Track your marketing channels performance in the personal area, or pass information to Google Analytics. You can collect information about the number of visitors, interactions with the site, lead source, and much more.

Pre-built calling widgets

Boost your website conversion with Callback and Click-to-call widgets. The solution is easy to install - just generate code in the personal area, embed it on the website and get ready to receive calls.

Use Cases

Improving internal communication with CRM

Connect your PBX to popular CRM systems for free. Teamsale, HubSpot, Pipedrive and many other integrations are already available. Log calls, use the built-in dialer, and track every interaction with a client online.

Automating call center with AI platforms

Connect ElevenLabs, VAPI or Retell AI and use voice agents for answering or making calls. You can handle more requests or even implement around the clock support without hiring additional staff.

Call flow management

Use Zadarma free PBX to define how calls are routed - from simultaneous ringing on multiple devices to call queues. Additionally, configure IVR, record calls, set up voicemail and use other helpful features. Everything is managed online and can be adjusted anytime.

Reaching international clients

We have over 30,000 virtual numbers in stock. Provision DID in less than 1 day and enjoy low rates for international calls.

Switching from GSM to VoIP

Tired of physical phones and SIM-cards? We got you covered! Benefit from VoIP telephony features without changing the number. Porting is already available in 40 countries. Check the coverage here and start the process today.

Ready to try a SIP trunking solution from a top VoIP provider?

Whether you’re building a global call center or just getting started, our pricing keeps things clear and flexible.

Payment: Monthly Annual

Transparent price plans One payment for the whole team Price plan region Choose region Choose region Standard Office Corporation	Standard $0 / month Activate	Office $39 / month Activate	Corporation $79 / month Activate
tariff_pkg_unlimited_call_usa_canada
Free outgoing minutes (including United States)	0	100500	101000
Virtual phone numbers	0	4	8
tariff_pkg_tollfree_numbers	0	1	2
PBX and CRM users	5	10	20
Per-second billing for outgoing calls
Free integrations with popular CRM and AI systems
24/7 Customer support (chat, tickets, phone)

More details about the price plans

Transform Your Business Communications Today

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Frequently Asked Questions

SIP trunk is an interconnection that allows to connect your phone system (PBX) to a public telephone network using Session initiation protocol (SIP) and internet.

Zadarma does not require any special equipment. You can connect any software/hardware that works on SIP protocol to our system, including self-hosted or cloud PBX from third party providers (Asterisk, 3CX, FreePBX, etc). If you don’t have a PBX yet, you can create it in Zadarma and configure apps or IP phones for calling.

Zadarma offers number porting in 40 countries. You can check the porting coverage here. If your country is on the list, you can transfer the number to Zadarma and use it within our system.

The limit of outgoing channels depends on the price plan. Standard and Economy plans offer 3 channels for a SIP login. The number of outgoing channels in the paid Office and Corporation bundles may vary by region; see each bundle’s description for details. Corporation plan can be expanded up to 20 times, so any team can find a package that suits them.

With Zadarma, it is. We highly value the security of our users, so we continuously introduce features that protect you. You can use TLS transport with SRTP encryption, restrict calls by IP, get email alerts if the system detects suspicious activity on the account and fully control your setup through a personal area.

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SIP trunk for business

What is a SIP trunk?

Who needs SIP trunk