An increasing number of companies no longer want to operate their corporate telephony via local (on-premises) telephone systems, but want to switch to a solution in the cloud. In fact, however, there are two technically very different models for pure online solutions: IP-Centrex and hosted PBX.

Common feature of both models: location-independent telephony

Both solutions are virtual telephone systems that use the SIP protocol to digitally transfer telephone calls via an IP connection over the Internet. Nothing changes in the practical application: you continue to dial the number on the phone as usual and reach your call partner.

In general, cloud solutions enable you to benefit from location independence, because users can access the virtual system from anywhere in the world and use it to make phone calls. Furthermore, users have great freedom in the choice of device types: Calls can be accepted not only via the classic desk phone but also via a smartphone app or softphone.

Both IP-Centrex and the hosted PBX have been adapted to each other in the application, many functions are available in both the one and the other solution. Nevertheless, you should find out in advance which technology a provider relies on.

Therefore, it is particularly important to know exactly what you expect from your corporate communications before making a purchase: Would you like to be able to integrate many extensions and are you satisfied with the standard scope of services of a telephone system? Or do you want to design your system individually, keep it flexible and benefit in particular from the higher security aspect?

IP-Centrex: Cost savings through shared server use

Centrex stands for “Central Office Exchange”, meaning that the installation is provided on the public network by a provider. All customers of this provider use the same system. Users are only distinguished by their access data. This means, for example, that maintenance and operating costs can be distributed among several users.


In practice, the situation is therefore as follows: You pay a fixed amount per workstation or per extension and month. Your provider will create accounts for you on his large telephone system. However, you share these with many other customers. And: You obtain the complete telephony and also the telephone system from only one provider.

Advantages and disadvantages

Advantages of the IP Centrex Model

  • existing standard functions such as forwarding, holding or toggling
  • Automatic update of the telephone system
  • easy handling and administration
  • Low cost of deploying small numbers of users
  • better integration: telephony and telephone system run from the same provider

Disadvantages of using an IP-Centrex solution

Despite the advantages, the possibility of customising the telephone system is limited.

Another important point that speaks against an IP Centrex solution is that many customers use the same instance, which makes this model more fragile in terms of data protection and reliability. For example, if an IP Centrex server fails, all customers registered there are offline. This can also happen, for example, if another user overtaxes the system.

Since you pay a fixed amount per user, the fixed costs also increase linearly with the number of employees. This quickly results in a high basic fee.

Hosted PBX: Individual systems on own server

An alternative to IP-Centrex models are cloud-based telephone systems to which only you and your employees have access to the server dedicated to you: so-called hosted PBX.

You receive all the functions of a local PBX, but also have the advantage of being independent of location. Administration and maintenance take place virtually via the Internet browser in the cloud. A hosted PBX is much more secure than an IP-Centrex, because you get more control over your own instance and can restart or completely reset the server on your own. You are independent of the usage behavior of the other participants.

Advantages and disadvantages

Benefits of using a hosted PBX

  • fair price-performance ratio in operation, even with larger company sizes
  • Flexibility in the number of users
  • more control over your own instance
  • higher security with regard to data protection
  • higher reliability
  • more freedom in the use of the server

Disadvantages of the model

  • more complicated to set up and administer
  • higher acquisition costs
  • manual import of updates
  • manual integration of the SIP trunk provider

easybell Cloud telephone system: all the advantages in a PBX

Our cloud PBX is also a hosted PBX, which makes your enterprise telephony secure: you get your own installation on a separate server (VM). With this dedicated version you don't have to share your PBX with other users. Your telephone system is available to you at all times.

Furthermore, it is as easy to set up and operate as an IP Centrex system. Using your easybell account, you can easily administer the cloud telephone system yourself in the easybell customer portal. As soon as an update or a new feature appears, it is automatically activated in your cloud telephone system. You don't have to worry about updates yourself.

In addition, a decisive technical advantage of our hosted PBX is the risk diversification in the event of a server failure. If one of our instances should fail, this has no effect on the others. Even if a host (physical server on which several cloud telephone system instances are running) fails, the failed instances are restarted within a short time on an alternative machine.

There are no costs involved in setting up your easybell cloud telephone system. However, they do not pay per workstation either, but receive a quota for several extensions. This means that with a monthly requirement of five to ten extensions, the costs are significantly lower than with a classic IP-Centrex solution.

And thanks to encrypted metadata and encrypted telephony, communication via easybell's hosted PBX is tap-proof.

Author: Julia Jünger
Last edited on: 18. May 2021