Mexico: SIP providers and connecting a number to the PBX

We do not issue numbers: the venue buys a Mexican number from a carrier and brings it into its own PBX as a trunk. The steps that are the same everywhere — trunk modes, form fields, network and the connectivity test — are described in the overview «Connecting a provider's number to the PBX»; this page covers only what is specific to Mexico: where to get a number, what that provider issues and what of it goes into the admin panel.

The data on this page was collected on 9–10 September 2026 from the providers' own documentation, PBX vendor compatibility matrices and regulator materials; links are in the «Sources» section.

In brief#

• What sets Mexico apart is not codecs or encryption but the way the trunk is delivered. The large carriers (Telmex, Totalplay, Alestra/Axtel, Metrocarrier, Coeficiente) hand over a «troncal SIP» not over the internet but through their own equipment on the venue's premises: the PBX sees their border server at an internal address such as 10.x.x.x. A cloud PBX physically cannot reach such a trunk — that rules out half the market straight away.
• The first candidate is Enlaza Comunicaciones (siptrunk1.enlaza.mx, registration, UDP 5060): the only Mexican carrier that publishes its trunk parameters openly, together with a ready-made Asterisk configuration. Next come NGX Networks (certified by the PBX vendor 3CX, supports both registration and IP authentication, numbers in 70+ cities) and Convergia México (IP authentication only and a static public address required — exactly our case).
• Almost nobody in the country publishes parameters. Of the fifteen providers reviewed, two name their server address openly; with the rest everything arrives by email after the contract is signed. That is the state of the market, not a gap in this guide.
• Ask about codecs before you sign: Mexican configurations often have G.729 as the default, while the PBX speaks G.711 and G.722. The provider AJTEL goes further and requires mandatory encryption — that trunk will not come up with our PBX at all.
• Every provider has its own dialling format. Enlaza, for example, expects outbound numbers with the 49786 prefix, otherwise «las llamadas serán rechazadas»; a format mistake produces a rejection, not silence.
• The number is issued to a taxpayer. You need an RFC and a Constancia de Situación Fiscal (a tax-status certificate from SAT) — with local carriers and international ones alike. A foreign company without a Mexican legal entity will usually not be sold a geographic number.

Numbers in the country#

The country code is +52. Since 3 August 2019 the country has used a single ten-digit dialling plan: the 01, 02, 044 and 045 prefixes were abolished, the split between «local» and «long-distance» numbers was removed, and when calling a mobile from abroad the leading «1» is no longer needed. Inside the country a number is dialled as ten digits with no prefixes at all; the international prefix for calls out is 00. In «Lines» the number is entered as +52 plus ten digits.

• The number is an area code plus a subscriber part, exactly ten digits in total. Only three metropolitan areas have two-digit codes: 55 (Valley of Mexico), 33 (Guadalajara), 81 (Monterrey). Other cities have three-digit codes: 656 — Ciudad Juárez, 998 — Cancún, 722 — Toluca.
• Mobile and landline numbers are not told apart by a prefix — both categories live in the same ten-digit space and are dialled identically. For billing the difference does exist: at NGX, for instance, «México Fijo» costs 0.15 MXN per minute and «México Celular» 0.35 MXN.
• The mobile «1» was dropped from dialling but is alive in SIP. Enlaza requires mobiles to be sent as 49786 521 XXXXXXXXXX and landlines as 49786 52 XXXXXXXXXX. Every provider has its own outbound format — check it before you go live.
• Toll-free for the caller is the 800 range. Both local carriers and international services sell them.
• Emergency calls are 911, with 089 (anonymous reports) and 072 alongside. Local providers include them in the service.
• The form the number arrives in on an incoming call:

⚠️ Seven digits against ten. The PBX compares the last seven digits, while a Mexican number has ten: the area code and the start of the number take no part in the comparison. Two numbers from different cities with the same ending (55 12 34 5678 and 656 123 4567) will collapse into one line. Within a single city that cannot happen; when opening a second venue in another state, compare the endings of the numbers when ordering.

Who issues a number with a SIP trunk#

The first four rows are the providers with a «What to enter in the admin panel» table below (Nextor's parameters come by email, so it sits in the collapsed block). The rest either disclose credentials only after a contract or run on an architecture a cloud PBX cannot reach.

Enlaza Comunicaciones#

A carrier from Mexico City (legal entity Conexión y Enlace de Comunicación Profesional S.A. de C.V.). The only Mexican provider that publishes its trunk parameters openly — its site carries a provisioning manual with a ready-made Asterisk configuration. Inbound and outbound are two separate products: you can buy either one, and if you buy both you create two trunks in the admin panel with different addresses.

What to enter in the admin panel (Telephony → «Trunks and connections» → «Add provider» → the «SIP trunk (custom provider)» card):

What to set up at the provider: choose the product (inbound, outbound or both) → obtain the login, the password and the list of numbers → top up the prepaid balance, without it outbound calls do not work (the balance is visible in the provider's billing portal) → ask them to put G.711 first: their codec list starts with G.729, which the PBX does not understand.

Pitfalls ⚠️ Outbound calls only go out with the 49786 prefix: 49786 + 52 + ten digits for landlines and 49786 + 521 + ten digits for mobiles, otherwise the provider rejects them. The prefix is added by a rule on the «Outbound» tab; if the rule does not help, write to our support. Enlaza accepts a caller ID override only in a separate SIP header, Remote-Party-ID, which the PBX does not send by default — the «Present as» field will not work on this trunk, so agree the number with the provider and fix it in the contract. The manual itself is dated January 2020: confirm the server addresses and the prefix with support before going live.

Source: Manual de configuración Troncales SIP (PDF) · enlaza.mx — 09.09.2026.

NGX Networks#

A Mexican carrier with its own round-the-clock network operations centre and 3CX certification for Mexico. The most «cloud-friendly» of the local ones: it states compatibility with hosted PBXs outright and issues a separate registration address for them. Tariffs are public — unlimited from 450 MXN per channel (Mexico), per minute from 0.15 MXN to landlines and 0.35 MXN to mobiles; numbers in 70+ Mexican cities, the USA and 85+ countries, with porting supported.

What to set up at the provider: choose the mode (registration or an address allow list) → pass them the static IP of our PBX from the «Server» tab, it is needed in both modes → order numbers in the cities you need → require G.711 a-law/u-law in the codec list → clarify the form the number will arrive in on incoming calls.

Pitfalls ⚠️ Access is granted by an address allow list («solamente damos acceso a tu IP») even with registration: if the dedicated PBX is recreated the address changes and the trunk quietly dies — submit the new address in advance. Their registration addresses differ for on-premise and hosted PBXs, so ask which one is yours. The «unlimited» tariffs are subject to a fair-use policy — read the terms if you plan outbound campaigns. On outbound calls you may present only numbers from your own account. Codecs are not published — that is a deal condition, not a detail.

Source: Troncales SIP en México · the 3CX matrix for Mexico — 09.09.2026.

Convergia México#

A carrier operating in Canada, the USA, Mexico and Colombia, and the only 3CX «preferred» partner in the country — that is, a technical and commercial partnership rather than merely «tested». It has no self-service portal: provisioning goes through the sales department only, on a contract with a Mexican legal entity.

What to set up at the provider: give them the public address of our dedicated PBX — it is on the «Server» tab, the «Static IP» field → point the purchased numbers at the trunk → request G.711 priority → if needed, order permission to present another number on outbound calls (with them it is a separate request; by default only account numbers are allowed).

Pitfalls ⚠️ IP authentication does not survive an address change: if the dedicated machine is recreated the trunk dies silently until the provider updates its allow list. There is nowhere in the form to enter the backup SIP server — one trunk equals one address; if you need the backup, add it as a second trunk. The main trunk number is entered with them in national format (ten digits; the 3CX documentation example is 7778811960), not in international format. Codecs are not published — demand G.711 a-law/u-law in writing before signing.

Source: Convergia — CxC SIP Trunking · the 3CX matrix for Mexico — 09.09.2026.

Telxi#

An international provider with a self-service portal that made the 3CX list specifically for Mexico. Its parameters are public and sign-up takes minutes. ⚠️ No Mexican numbers are declared in its coverage — only the USA, Canada, the UK and Europe: in Mexico it works as a trunk for outbound calls and for calls incoming to a foreign number, but you cannot build a local presence for the venue on it. Check for Mexican numbers by searching in its portal.

What to set up at the provider: sign up in the portal → pass the document checks → create a trunk and take its ID and password → check whether Mexican numbers appear in the search → put PCMA/PCMU (that is G.711) first, because their codec list also contains G.729 and Opus, which the PBX does not understand.

Pitfalls ⚠️ Numbers are entered in their portal in the international +52… format. For a Mexican venue this is a trunk «for later»: an emergency 911 call will not work through a foreign provider, and incoming calls will arrive on a number in another country.

Source: Telxi — How to connect your SIP Trunk to 3CX or other PBX · the 3CX matrix for Mexico — 09.09.2026.

Providers whose parameters come with the contract#

Carriers that will not work with our PBX#

International providers with Mexican numbers#

Mexican numbers are sold by the large international services — Twilio, Telnyx, DIDWW. The Telnyx and Twilio cards are already in the catalogue when adding a provider: the server address and mode are filled in for you.

• What they sell. Twilio offers all three types of Mexican numbers: geographic, mobile and toll-free 800. Mexico is in the published DIDWW coverage and in the Telnyx list of countries with inbound calling; which number types are actually available with those two is best checked by searching in the portal.
• The paperwork is stricter than in Europe and depends on the number type. For a geographic number Twilio requires an address inside the area code of the number (a PO box is not accepted) and a Constancia de Situación Fiscal; for a mobile — an address in Mexico and an RFC; for a toll-free 800 — an address anywhere in the world and business registration documents. In other words, 800 is practically the only Mexican number available to a foreign company without a local legal entity.
• A Mexican mobile number is for person-to-person use only. Carriers in the country do not pass automated campaigns and application-to-person messaging to such numbers, as Twilio warns outright. For a venue's public number take a geographic one, not a mobile.
• Emergency calls do not work through an international provider. With them 911 is either a separate service or absent, while Mexican carriers include 911, 072 and 089 in the service. For a restaurant or a shop this is a real argument for a local provider.
• The trunk parameters of these providers are the same in every country and are covered in the catalogue cards — see «Add provider»; they have no Mexico-specific settings.

Porting a number#

• Porting in Mexico is free and is a subscriber's right. The number portability rules and the numbering plan were adopted as one package in 2018; the application is filed by the receiving carrier at your request, and the donor carrier files nothing.
• What providers offer. Porting is declared by NGX Networks (national and international), AJTEL (Mexico, the USA and Canada), Coeficiente, CloudCall and Itel. Look up the timescales and the document list in the specific provider's contract: according to provider data as of September 2026 they differ from one to another.
• A number in an individual's name is possible — Mexican providers do invoice individuals with an RFC, but for a geographic number they will still ask for the tax-status certificate.
• After porting, check the service address with the new provider: that is what is passed to the 911 emergency service.
• Changing the public address of our PBX breaks any IP-authenticated trunk (Convergia, and the address mode at NGX and Nextor) — when the dedicated machine is recreated, give the provider the new address in advance.

Rules and paperwork#

If it does not work#

1. The trunk does not come up at all and the credentials contain an address like 10.x.x.x. This is a Telmex, Totalplay, Alestra, Metrocarrier or Coeficiente trunk: it lives inside the carrier's network and is unreachable from the cloud. Ask the carrier for a connection over the internet to a public address, or take a trunk from a provider in the table above.
2. The provider points you at an encrypted port. Encryption is not supported for trunks — ask for a plain UDP account. AJTEL does not have one at all; that is a condition of their service.
3. The call connects but there is silence. Mexican configurations often list G.729 first, while the PBX speaks G.711 and G.722. Ask the provider to put G.711 a-law/u-law at the top of the list.
4. Outbound calls are rejected while inbound ones work. Most likely the dialling format does not match: Enlaza expects 49786 before the number (49786 52… for landlines, 49786 521… for mobiles), other providers have their own. Add the prefix with a rule on the «Outbound» tab and confirm the format with the provider.
5. Enlaza outbound calls are silent although the credentials are correct. Their outbound trunk is strictly prepaid: at a zero balance calls are not released. Check the balance in their billing portal.
6. The wrong number is presented on outbound calls. Enlaza accepts an override only in a separate SIP header that the PBX does not send by default; Convergia and NGX allow only numbers from your account. The «Present as» field will not work on such trunks — write to our support, the mode is enabled on the server side.
7. It worked and then stopped after the PBX was recreated. At Convergia, and in the address mode at NGX and Nextor, authentication is by IP: the new address must be added to the provider's allow list. The address is on the «Server» tab, the «Static IP» field.
8. A call to the second number follows the scenario of the first. The last seven digits matched — with ten-digit numbers from different cities that is possible. Order numbers with different endings, or handle both with a single routing rule.

Causes that do not depend on the country are in «If calls do not get through»; network and codec requirements are in «Network and compatibility». A SIP trace in the trunk menu helps to pick a specific call apart.

Frequently asked questions#

Can I get a Mexican number if the company is registered outside Mexico?#

A geographic one — almost certainly not: both local carriers and international services ask for an RFC and a tax-status certificate, and for a geographic number also for an address inside its area code. The realistic option for a foreign company is a toll-free 800 number from an international provider: for that an address in any country and business registration documents are enough.

Why can't I use a trunk from Telmex or Totalplay — they are the largest carriers?#

Because their trunk is delivered through their own equipment on the venue's premises and lives inside the carrier's network: the PBX sees the server at an address such as 10.x.x.x. Our PBX sits in the cloud and cannot get into that network. The same applies to Alestra/Axtel, Metrocarrier and Coeficiente — that is, to most of the big names in the country.

Registration or IP authentication — which to choose?#

Registration, if the provider supports it: it does not depend on allow lists. IP mode is mandatory at Convergia and available at NGX and Nextor. Either way you need a dedicated PBX with a static address — it has one, and the value is on the «Server» tab. Remember that after the machine is recreated the address changes and must be given to the provider again.

What is the 49786 prefix at Enlaza and is it mandatory?#

It is: the provider only accepts outbound calls with it — 49786 plus 52 plus ten digits for landlines, 49786 plus 521 plus ten digits for mobiles. Without the prefix calls are rejected. The prefix is added by a rule on the «Outbound» tab; it does not affect inbound calls, where the number arrives as 52 plus ten digits.

How do I dial 911 through the PBX?#

You cannot: emergency numbers are shorter than four digits, while outbound rules work from four. Keep a mobile phone on shift. Note as well that with a number from an international provider emergency calling does not work at all, whereas Mexican carriers include 911, 072 and 089 in the service.

How long does provisioning take?#

With providers that have a self-service portal (Telxi, IPComms) — the day you apply. With Mexican VoIP providers — from the same day to a week if the paperwork, the RFC and the tax-status certificate are ready. With the large carriers — weeks, with an engineer visit, and such a trunk still will not connect to a cloud PBX.

Sources#

All links checked on 09.09.2026.

Providers

• Enlaza Comunicaciones — SIP trunk configuration manual (PDF): https://enlaza.mx/wp-content/uploads/2020/02/Manual-de-configuracion-troncales-SIP-Enlaza.pdf · website: https://enlaza.mx/
• NGX Networks — SIP trunks in Mexico: https://www.ngxnetworks.com/en/troncales-sip/
• Convergia — CxC SIP Trunking: https://convergia.io/es_ES/voice-cxc-sip-trunking/
• Telxi — how to connect your SIP trunk to 3CX or another PBX: https://intergo.freshdesk.com/support/solutions/articles/43000707929-how-to-connect-your-sip-trunk-to-3cx-or-other-pbx
• Nextor Telecom — SIP trunks for Asterisk: https://nextor.io/x_1/troncales-sip/troncales-sip-para-asterisk-en-mexico/ · pricing: https://nextor.io/x_1/troncales-sip/troncales-sip-precios/
• Itel — SIP trunk for business: https://itel.mx/telefonia-fija/troncal-sip-empresas · CloudCall: https://conmutadores.com.mx/troncales-sip.php · Intelisipco: https://intelisipco.com/troncales-sip/ · IPComms (Mexico): https://www.ipcomms.net/es/mexico/
• AJTEL Comunicaciones — SIP trunks and encryption terms: https://ajtel.net/W/sip/
• Telmex — Troncal IP: https://telmex.com/web/empresas/troncal-ip-telmex · Totalplay Empresarial: https://totalplayempresarial.com.mx/voice/sip-trunks · Alestra — SIP for Business: https://www.alestra.com.mx/soluciones/sip-for-business/ · Metrocarrier: https://www.metrocarrier.com.mx/telefonia/ · Coeficiente: https://coeficientemx.com/servicios/telefonia/troncal-sip
• The 3CX compatibility matrix for Mexico (Convergia, NGX, Telxi, Twilio): https://www.3cx.com/partners/sip-trunks/mexico/

Regulator, numbering and law

• Ley en Materia de Telecomunicaciones y Radiodifusión, published in the DOF on 16.07.2025: https://dof.gob.mx/nota_detalle.php?codigo=5763167&fecha=16/07/2025 · the text of the act (PDF): https://www.diputados.gob.mx/LeyesBiblio/pdf/LMTR.pdf
• Ten-digit dialling since 03.08.2019: https://www.ift.org.mx/comunicacion-y-medios/marcacion-a-10-digitos · regulator statement 34/2019 (PDF): https://www.ift.org.mx/sites/default/files/comunicado_34_ift.pdf
• The numbering plan and number portability rules, DOF 11.05.2018: https://www.dof.gob.mx/nota_detalle.php?codigo=5522388&fecha=11/05/2018
• The personal data protection act (PDF): https://www.diputados.gob.mx/LeyesBiblio/pdf/LFPDPPP.pdf
• The REPEP registry (PROFECO): https://repep.profeco.gob.mx/

International providers

• Twilio — document requirements for Mexican numbers: https://www.twilio.com/en-us/guidelines/mx/regulatory · Telnyx — coverage: https://telnyx.com/global-coverage · DIDWW — coverage: https://www.didww.com/coverage

Related pages#

• Connecting a provider's number to the PBX — the common steps, trunk modes, network and the connectivity test.
• Setting up SIP phones — how to connect desk phones and DECT handsets to extensions.