What exactly is a SIP number?

Updated 2026-09-30 · By the SMS Conecta team (SMSConecta Inc.)

Short answer: A SIP number is just an ordinary phone number whose calls travel over the internet via SIP (Session Initiation Protocol), the open standard that softphones, office phone systems and call centers run on. People dial it exactly like any other number, and you pick up on any SIP app, desk phone or PBX registered with a server address, username and password.

A SIP number is simply a normal phone number whose calls travel over the internet via SIP, the standard protocol underpinning softphones, office phone systems and call centers. Callers dial it the usual way; you answer through any SIP-capable app or device.

What SIP stands for

SIP is short for Session Initiation Protocol, the open standard phone apps and phone systems rely on to set up, ring, answer and end calls over an internet connection.

Being a standard means you're never locked into a single app. Any SIP-compatible softphone, desk phone or PBX can register against the same account.

How it actually works

When someone dials your number from a mobile or landline, the call hits your provider through the ordinary phone network. The provider then routes it over the internet to whichever device is currently registered to your SIP account.

Your app registers using three pieces of information: the SIP server address, a username and a password. Once registered, the app shows up as online and your number rings there. Outgoing calls follow the same path in reverse.

What you can hook up

Softphones: Zoiper, Linphone, MicroSIP, Bria and other SIP apps across Windows, macOS, Android and iOS
Office phone systems: 3CX, FreePBX, Asterisk and comparable PBX software
Call-center and helpdesk setups built around SIP trunks or SIP accounts
Hardware desk phones with SIP support
An ordinary mobile or landline, through call forwarding

Connecting a softphone in 3 steps

Open your number's page in the SMS Conecta dashboard and copy the SIP server, username and password.
In your softphone, create a new SIP account and paste those three fields exactly as shown.
Save it. The status flips to green or 'registered' once connected, and calls to your number will ring in the app.

Hooking up a PBX

In a PBX like 3CX, FreePBX or Asterisk, add the number as a SIP account or trunk using that same server, username and password. From there you route incoming calls to an extension, ring group or IVR menu, and pick which outbound calls go out under this number.

This setup lets a whole team share a single public number, with calls spreading out to whoever is free.

Who actually uses SIP numbers

Remote teams rely on a SIP number so anyone can pick up the company line from a laptop, regardless of location. Small businesses hook one into a PBX to gain extensions, ring groups and an auto-attendant menu without installing physical phone lines.

Individuals use SIP too: a softphone on a laptop makes it easy to take calls on a foreign number while travelling, without juggling SIM cards or paying roaming for incoming calls.

Developers and IT teams favour SIP precisely because it's open. They can test call flows in Asterisk or FreePBX and move between apps or systems freely, without changing the number itself.

SIP number versus a mobile SIM

	SIP number	Mobile SIM
Location	a SIP number works anywhere you have an internet connection	a SIM is limited by local coverage and roaming
Devices	a SIP account can register on several apps at once	a SIM lives in one phone
Team use	a SIP number can ring a PBX and several people	a SIM rings a single person
Continuity	a SIP number survives a broken or stolen phone	—

Can a SIP number receive SMS?

SIP itself mostly deals with voice calls, and a lot of SIP apps don't handle text at all. With SMS Conecta, SMS to your number land in the online dashboard live, separately from calls, so you get both without any extra setup.

Fixing registration and call issues

Won't register: re-copy the server, username and password; a stray extra space is a common culprit
Registers but doesn't ring: check only the intended device is set to answer, and that the app is allowed to run in the background on mobile
One-way or missing audio: usually a router or firewall problem; try a different network, or turn on the app's NAT or STUN setting
Mobile app misses calls while idle: enable push notifications or keep the app running, depending on the app
Easiest fallback: turn on forwarding to your regular phone while you troubleshoot

What comes bundled with an SMS Conecta number

Every SMS Conecta number includes SIP credentials, forwarding to any phone, a browser dialer, unlimited incoming calls and SMS, plus 500 outgoing SMS and 1,000 outgoing minutes a month. Plans start from $1.80 per month, billed yearly ($21.60 per year), across all 181 countries.

Every number carries a 7-day replacement guarantee, so if an app won't accept it, you get a fresh one free. If it hasn't been used for any call or SMS, a full refund is available within 7 days, and you can keep it for as long as you like.

Included on every plan

Unlimited incoming SMS
Unlimited incoming calls
500 outgoing SMS per month
1,000 outgoing minutes per month
SIP credentials, call forwarding and web dialer
Keep your number as long as you want
Works with WhatsApp, Facebook, Google, Telegram and thousands more
7-day replacement guarantee — free new number if it doesn't work for you
7-day money-back guarantee if the number is unused

Numbers start at $1.80 per month, billed yearly ($21.60 per year). Settle up with USDT or USDC.

Frequently asked questions

Do I need special hardware for a SIP number?

No. A free softphone app on your computer or phone is enough. SIP desk phones and PBX systems remain optional extras.

Can one SIP number ring multiple devices?

Yes. Register the same SIP account across several apps, route it through a PBX, or pair SIP with call forwarding.

Can a SIP number take SMS?

SMS Conecta numbers receive SMS inside your online dashboard, kept separate from SIP calls.

Is a SIP number a genuine phone number?

Yes. SMS Conecta numbers are real numbers on national networks. Anyone can dial them from an ordinary phone; SIP is simply the mechanism that delivers the call to you.

What details do I need to configure SIP?

Three things: the SIP server, your username and your password, all shown on your number's page in the dashboard.

Which SIP apps are compatible?

Any standard SIP client, including Zoiper, Linphone, MicroSIP and Bria, plus PBX systems like 3CX, FreePBX and Asterisk.

Why is there no audio on my SIP calls?

Usually a network or firewall hiccup. Try a different network or turn on NAT or STUN settings inside your app.