SIP • Last Updated 5/17/2024

What does non-fixed VoIP mean?

Non-fixed VoIP numbers are assigned to a user rather than a phone line. Here’s what you need to know:


By Fiona McDonnell

woman talking on non-fixed VoIP phone

You can’t tell the difference between a fixed VoIP and non-fixed VoIP number from appearance alone. But there’s a key difference between fixed VoIP and non-fixed VoIP numbers: a fixed VoIP number is attached to a physical address, and a non-fixed VoIP number is not restricted to any physical address.

This difference is simple enough. However, there are nuances to take into account when choosing the type of VoIP number to fit your needs.

What is non-fixed VoIP?

One of the defining features of a VoIP number is that VoIP numbers are assigned to users, rather than addresses or devices. But this type of VoIP number is actually a non-fixed VoIP number. Non-fixed VoIP numbers are sometimes called virtual phone numbers.

Non-fixed VoIP phone numbers are easily assigned: users can often get a non-fixed VoIP number with just an email address and a payment method. That’s why most phone numbers assigned on services like Google Voice and Skype are non-fixed VoIP phone numbers.

Non-fixed VoIP numbers can be created with any area code or country format. This is quite handy for businesses that have many employees or call centers spread across a large area. Wide-spread businesses like this often choose non-fixed VoIP numbers with local area codes as their customer service phone numbers; customers then dial a local number to reach the business, no matter where the business is physically located.

Non-fixed VoIP numbers also enable businesses to quickly and easily add new phone numbers as their teams expand, downsize or transition to working from home.

The downside of non-fixed VoIP numbers is that they’re usually viewed as less authentic than fixed VoIP numbers.

Since non-VoIP numbers are so easily created and have no associated physical address, non-fixed VoIP numbers are frequently not accepted for creating business accounts with service providers. Additionally, non-fixed VoIP numbers are often used by scammers and spammers, since people are more likely to answer a call from an unknown caller if the number appears local.

Most of the time, however, end users can’t tell the difference between a fixed VoIP number and a non-fixed VoIP number. The differences mostly affect the person or business that purchased the phone number.

How non-fixed VoIP works

A non-fixed VoIP number transmits calls entirely or almost entirely over the internet (occasionally VoIP calls may use the PSTN as part of the connection path).

The analog audio from the phone call is converted into data packets and transmitted over the internet. The data is converted back into an audible voice signal once the audio data reaches the receiving device.

Information about the calling phone number—the phone number itself and the caller name assigned to that VoIP phone number—is transmitted in the CNAM (Caller Name) tag. Receiving devices display the CNAM information as part of the caller ID service.

Most of the time, non-fixed VoIP numbers are assigned to devices like smartphones, VoIP phones and computers. The all-internet connection of non-fixed VoIP numbers is very well-suited to those sorts of internet-capable devices. Analog devices are most often assigned a fixed VoIP number or traditional phone number.

How does non-fixed VoIP differ from fixed VoIP?

In addition to being assigned to a specific geographic location, fixed VoIP phone numbers often connect to the Public Switched Telephone Network (PSTN) through a SIP trunk.

Non-fixed VoIP numbers can also connect to the PSTN through a SIP trunk, but, most often, non-fixed VoIP numbers do not rely on that legacy telephone network.

Additionally, fixed VoIP numbers are not as easy to get as non-fixed VoIP numbers, since a fixed VoIP number has an assigned physical address. So fixed VoIP numbers are typically treated as more authentic than non-fixed VoIP phone numbers. That’s why fixed VoIP phone numbers are a better choice in certain use cases.

Who uses non-fixed VoIP

The end users for most non-fixed VoIP phone numbers use the numbers for personal purposes, like Skype calls. However, the business use cases for non-fixed VoIP numbers are more diverse than the personal use cases.

These are some of the most common business use cases for non-fixed VoIP numbers:

Call centers

Call center providers like MAP Communications, Five9, and Answer National use non-fixed VoIP numbers to build call center teams on-demand. These call center teams can be located anywhere, and the call center provider simply provides non-fixed VoIP numbers that match the local area codes where most inbound calls come from.

In use cases like this, non-fixed VoIP numbers enable businesses to quickly build teams—employing team members all over the world—without paying the huge overhead for a physical location.

OTT communication apps

Skype and Google Voice came up earlier in this article, but there are other OTT communication apps that use non-fixed VoIP phone numbers. Facebook Messenger, WhatsApp and other apps use non-fixed VoIP numbers to provide voice communication inside the app.

Users that create an account with only an email address can still make voice calls in the app using a temporarily assigned non-fixed VoIP number. Another option is that a non-fixed VoIP number can be used to make it appear as though a user is calling from their landline or personal cell phone number.

Managed service providers (MSP)

MSPs that offer phone services to their clients can use non-fixed VoIP numbers to quickly assign new phone numbers to clients, as long as the clients do not need a phone number with a fixed physical address. Since non-fixed VoIP phone numbers are relatively easy to configure, an MSP can give their clients a lot of control over how their non-fixed VoIP phone numbers are set up, which reduces the customer service workload for the MSP.

Non-fixed VoIP phone numbers

There are plenty of reasons to use a non-fixed VoIP phone number. Conversely, there are plenty of reasons why you might prefer a fixed VoIP phone number. You should consider the pros and cons of each type of phone number and choose the best type of number for your use case, rather than taking a one-size fits all approach.

Benefits of non-fixed VoIP numbers

The benefits of non-fixed VoIP phone numbers can broadly be summed up as ease of acquisition and flexibility, but here are some specifics. Non-fixed VoIP number are

  • Simple to provision. If you need to expand your number inventory to supply more phone numbers to your clients or end users, non-fixed VoIP phone numbers enable you to quickly provision more phone numbers and assign them to new users.
  • Quick to reassign to a new user or device. In addition to being easy to provision, non-fixed VoIP numbers are also easy to reassign. You can move a non-fixed VoIP number to a new user or device in just a few minutes.
  • Easy to configure. Setting up a non-fixed VoIP phone number is simple, and the CNAM tag on a non-fixed VoIP number can be edited with relative ease. So it’s very easy to set up a non-fixed VoIP phone number to look the way you want to call recipients.

Disadvantages of non-fixed VoIP numbers

Ease of acquisition and flexibility are great benefits. However, those benefits can actually work against you in certain situations. Phone numbers that can be very easily acquired and configured are also hard to trust. Non-fixed VoIP number are

  • Commonly used by scammers. Since non-fixed VoIP numbers are so easy to get, scammers and spammers often use non-fixed VoIP phone numbers for scams and robocalls. If a user blocks the phone number, the offending scammer can just get a new number.
  • People won’t be able to spot a non-fixed VoIP phone number just by looking at their caller ID. However, spam filters are more likely to block calls from non-fixed VoIP numbers or mark them as “scam likely” calls.
  • Not usable in some situations. Occasionally, you won’t be allowed to use a non-fixed VoIP phone number as the contact phone number on an account. Since non-fixed VoIP phone numbers are so easy to get and change, they are frequently considered too unreliable to use as a contact phone number.
  • Not ideal for emergency calls. Since non-fixed VoIP numbers do not have an assigned address, a non-fixed VoIP number is unreliable for making 911 calls. Most emergency calls from non-fixed VoIP phone numbers cannot be routed to the correct emergency call center, and emergency calls from non-fixed VoIP numbers cannot be traced to assist the emergency response.

Identifying a non-fixed VoIP number

It’s impossible to identify a non-fixed VoIP number simply by looking at the number. You need to get data from the phone number provider to determine whether or not it’s a non-fixed VoIP number.

A simple number lookup can tell you if a number is a fixed or non-fixed VoIP number. However, a number lookup will not give you any geographic information, and number lookups often rely on CNAM data to tell you the name—which can be easily manipulated— associated with a non-fixed VoIP phone number.

So a number lookup is usually not reliable for discovering who’s calling from a non-fixed VoIP phone number or where they’re calling from. Ultimately, tracing a non-fixed VoIP phone number is tricky, because a non-fixed VoIP number is not confined to any geographic location or device, but it can be done.

Tracing non-fixed VoIP numbers

Although tracing non-fixed VoIP numbers is tricky, it’s not impossible. Here’s a brief rundown of how to find out who owns a non-fixed VoIP phone number:

First, try a reverse phone lookup. Most aren’t free, but the costs are minimal. (Avoid the free reverse phone lookup services—they rarely provide usable information.)

If the reverse phone number lookup fails (or you simply don’t want to pay), here’s what to do:

  • Set up your caller ID to display the IP address of incoming calls, in addition to the caller name and number.
  • Check the calling IP address using your caller ID.
  • Look up the IP address. This will give you a general location, though it will not give you a specific physical address.

It’s very difficult to find a physical address for a non-fixed VoIP phone number. Getting the carrier information and a general geographic location via a basic VoIP number lookup is often enough for business purposes, but most of the time, you’ll need the assistance of a private investigator to find the physical address associated with a non-fixed VoIP number.

Non-fixed VoIP frequently asked questions

To make sure we haven’t missed anything, here’s a lightning round of frequently asked questions regarding non-fixed VoIP phone numbers:

Can you call a non-fixed VoIP Number?

Yes. You can make and receive using a non-fixed VoIP phone number. Non-fixed VoIP can even be configured to forward calls to other phone numbers.

What is a Pinger non-fixed number?

Pinger is a VoIP operator that provides non-fixed VoIP numbers for sending and receiving text messages for free. Pinger numbers are only usable using an iOS or Android app that supports Pinger VoIP numbers. Pinger non-fixed VoIP numbers are also non-traceable.

Do scammers use non-fixed VoIP?

Scammers frequently use non-fixed VoIP phone numbers. Non-fixed VoIP numbers are easy to replace if they get blocked, and non-fixed VoIP numbers can be manipulated to appear legitimate over caller ID.

Can you block a non-fixed VoIP number?

Yes. You can block a non-fixed VoIP number the same way that you’d block any other number on your device or through your telecom service provider.

Can you text a non-fixed VoIP number?

Yes. Non-fixed VoIP phone numbers can be configured to send and receive text messages.

Can you track a non-fixed VoIP number?

Non-fixed VoIP numbers can be tracked, but it’s challenging. Non-fixed VoIP numbers can easily be reassigned to a new device or user, so it can be very difficult to find out who’s making calls from a non-fixed VoIP phone number.

Contact our team of experts to learn what makes Telnyx the best VoIP provider.

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