Connecting a provider number to the PBX

Your own PBX in the admin panel can receive calls on your landline or mobile number as long as that number comes from a SIP provider — a telecom operator or a virtual telephony service that offers a "SIP trunk" (sometimes called "external PBX connection" or "SIP account for your own PBX"). The number stays with the provider, and calls to it arrive in your PBX: to staff on desk phones and in the app, to the voice bot, or to a greeting with a menu; conversations are recorded and appear in "Calls".

This page covers what is the same for any provider: the two ways to connect, which data you need, what to enter where, what the network must allow and how to tell that everything works. The specifics of individual operators are in the country guides at the end of the page.

Open: Admin panel → Telephony → "Trunks & pairings" tab (admin.cenaly.ru/telephony?tab=trunks).

When you need this and what is required#

You connect a provider when the venue has (or should get) an external number guests call, and you want to receive those calls in the PBX: on several phones at once, with a queue, recording and call analysis. If calls from the website and the app are enough for you, an external number is not required.

You will need:

1. A dedicated PBX for the location — the "Server" tab in the Telephony section. Provider trunks only work on a dedicated server: it has a static IP address you can give to the provider, and its own Asterisk configuration. The shared server is no longer offered to new locations.
2. A contract with the provider and the SIP trunk service (or a SIP account that allows connecting your own PBX). It is usually a separate tariff item; some operators offer it only to legal entities or only together with their own cloud PBX (such a provider will not work).
3. Trunk credentials from the provider's account — see "What to ask the provider".

Two trunk modes: REGISTER and IP auth#

The provider must somehow understand that a call to your number should be delivered to your PBX, and that a call from your PBX should be accepted and released into the network. There are two ways, and they are selected with one checkbox in the trunk form.

If the provider supports both modes, choose registration: it does not depend on allowlists and survives a server resize, during which the IP is kept but the provider may check both the address and the login.

What to ask the provider#

Before entering anything, collect from the provider (in the account, in the contract or from support) the answers to seven questions. Wording differs between accounts, so the usual names are listed alongside.

It is also useful to learn how many simultaneous calls (channels) the tariff includes, whether the provider allows substituting another number on outgoing calls (usually only the numbers of your contract), and whether it requires an IP allowlist for outgoing calls even with registration (it happens).

Step 1. Add the provider in the admin panel#

1. Open Telephony → "Trunks & pairings" and press "Add provider". If your operator is in the catalog (Zadarma, Telnyx, Twilio, MANGO OFFICE, Telfin, Sipuni, MTS Exolve, Netgsm, Verimor, FCN…), pick its card — the server address and the mode are filled in for you. For any other, use the "SIP trunk (your own provider)" card.
2. Fill in the form:

3. Press "Save". The trunk appears in the list with a registration status line.

Step 2. Test the connection#

In the trunk row press "Test connection". The wizard sends a real SIP request (OPTIONS) to the provider's server from the cloud and shows the reply: "server responded" means the address and port are correct and the path to the provider is open. This checks the address, not the login: whether the password is right is visible in the registration line.

Registration line states:

• "registered at provider" — the PBX has logged in to the provider's server; incoming calls should work.
• "no registration at provider" — the provider rejected the login or password, or does not allow this address. Check the credentials in the provider's account; after a password change the PBX re-registers on its own, incoming calls pause for a few seconds.
• "registration not needed (IP-auth)" — IP mode; check that the provider sees your address: make a test call to the number.
• "the PBX has not reported registration yet" — the server was just created or is restarting; wait a minute.

Step 3. Add the number and routing#

1. Open the "Lines" tab and add a line with the source "Provider trunk (DID)", choosing the trunk you just created. Enter the number as the provider issued it: the PBX compares the last seven digits of the number with what arrives in the call, so the format (+995 32 2… or 0322…) does not matter.
2. Leave the "Accepts calls" checkbox on. If you uncheck it on all numbers of a trunk, the PBX withdraws the registration at the provider and stops recognising its address — there will be no incoming calls at all.
3. In the "Routing" tab add a rule "call arrived on line … → where": to all operators, to a ring group, to the voice bot or to a greeting. Without a rule the call is handled by the default answer mode.
4. Call your number from a mobile and make sure the call arrives and audio works both ways.

Step 4. Outgoing calls and "Show as"#

Staff can call out through the same trunk. Open the "Outgoing" tab:

• switch outgoing calls on and assign each employee a default line (the number they call from) or add a pattern rule ("mobile numbers of the country → through this trunk, show number …");
• a rule can strip or prepend a prefix before sending to the provider if it expects the number in a particular format (for example 8… instead of +7…);
• the "Show as" field is the number the called party sees. Providers usually allow only the numbers of your contract; a foreign number is silently replaced with theirs or the call is rejected.

The PBX presents itself to the provider with the provider's own domain (From: <number>@<SIP host>) and the trunk login in Contact — as most operators require. If the provider insists on passing the number in the P-Asserted-Identity header, write to support: that option is enabled on the server side.

Network and compatibility#

The dedicated PBX sits in the cloud with a static address, so nothing is required from the venue's network — traffic flows between the provider and the cloud. Requirements for the provider:

If calls do not go through#

The SIP trace in the trunk menu — "Trunk diagnostics" — helps dig deeper: while the window is open, the PBX records the exchange with the provider and shows at which step the refusal happens.

Providers by country#

Below are guides for specific countries: who issues numbers with a SIP trunk there, in which mode, which parameters to enter and what to enable in the provider's account. The list is growing; countries without a link are in progress.

International providers with numbers in many countries (Telnyx, Twilio, DIDWW, Zadarma, sipgate, VoIP.ms…) are suitable when the local operator does not offer a trunk or you need a number from another country; they verify documents for the number more strictly (an address and business registration in the number's country).

FAQ#

Do I need a contract with the provider as a legal entity?#

It depends on the country and the provider. International number services sell to individuals but require proof of address for landline numbers; telecom operators almost always work with businesses under a contract. The country guides state this for every provider.

Can I connect several providers at once?#

Yes. Each provider is a separate trunk, each with its own number lines; routing and outgoing rules tell them apart. This is how venues combine a landline from the local operator with a mobile number from a virtual PBX.

What happens to calls when the server capacity is changed?#

The static IP moves to the new server and the registration at the provider is restored automatically; calls are possible the whole time except for a few seconds of re-registration. Providers with IP authentication need no changes — the address is the same.

The provider asks for a "SIP URI for forwarding" — what is that?#

That is the third way, without a trunk: the provider forwards calls from the number to the SIP address of your extension. It can be used when the provider has no trunk at all, but outgoing calls from the number will not work this way. In the admin panel there is the "Forwarding" line source for this — the wizard shows the address to enter at the provider.

Where are conversations recorded?#

All calls through the trunk are recorded the same way as calls to the app: recording, transcript and analysis are in the "Calls" section. The recording notice for the other party is enabled in the location settings.

Related sections#

• SIP phone setup — how to connect desk phones and DECT to extensions.
• The "Telephony" section in the admin panel: lines, routing, ring groups, outgoing calls.