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VoopIX is a system based on Voice over Internet Protocol (VoIP) technology that enables the transmission of voice communications over the Internet.


VoopIX is used to exchange telephone traffic over CARNET network, i.e. enables connectivity of remote member locations to a common telephone network and shared numbering, mobility of local extensions and free calls.

The core of VoopIX comprises 123 institutions and consists of five distributed servers in Zagreb, Split, Rijeka, Osijek and Dubrovnik.


CARNET system engineers
other AAI@EduHr users
faculties and colleges
other public institutions

How to Become a User

All full members of CARNET have the right to join the voopIX system. To be connected to the system, you must complete the Request for connection to the voopIX service and send completed and certified request by regular mail to the address of CARNET. Upon receipt of the request, CARNET representatives shall contact the facility representative to carry out a technical survey and examine all the details and possibilities related to the implementation of the connection, in order to optimally connect the facility to the voopIX system.

Although the use of VoopIX system is enabled to all full members of CARNET, the exceptions are those using VoIP service in which the telephone switchboard is moved to the telecom operator. An example of such services is CENTREX, as well as older telephone switchboards that do not have ISDN BRA or PRA connector, but older R2/MFC/PCM connections.

It’s simplest to connect a member who already has a VoIP-based (commercial or open-source solution) system, and it is much more demanding to connect an institution that has a classic ISDN port where additional hardware is needed. In this case, CARNET needs to examine, as a connection preparation, whereby a complete technical inspection of the entire installation, transmission and the same central unit is performed.

Questions and Answers

How to get more detailed information about this service?

When there is a member’s interest in the voopIX service, it is customary for the CARNET representative to make the presentation of this service and to explain all the details in direct contact with the representatives of the institution. On this occasion, a technical survey can be made of the connection possibilities at the location itself. The request is sent to the electronic address or by regular mail to CARNET, J. Marohnića 5, Zagreb.

Nevertheless, we can briefly say that the basis of the service is connecting the existing telephone exchange via a separate device to a shared private VoIP network, and then, if desired, additional IP phones can be installed and ultimately replace the old switchboard. The service is free for all full members of CARNET, and this device is also not charged for the facility. Also, there are no subscription or maintenance costs for this facility. In case the institution wants to have IP phones, it has to get them at their own expense.

Who is eligible for this service?

All full members of CARNET have the right of joining the voopIX system, based on the request  sent to CARNET.

How to establish a service?

Upon receipt of the request for connection, CARNET representatives shall contact the representative of the facility to conduct a technical survey and examine all the details and possibilities of the implementation of connection to optimally connect the facility to the voopIX system.

It is easiest to join a member who already owns a VoIP-based (commercially or open-source solution) system, and it is much more demanding to connect an institution that has a classic ISDN connection where additional hardware is needed. In this case, CARNET needs to conduct a survey, as a connection preparation, in which a complete technical inspection of the entire installation, transmission and the same central unit is performed.

Should a contract be signed?

There is already a membership agreement between all CARNET members and CARNET institutions, and as this is a service to which the institution is entitled under full membership, it is not necessary to sign a special agreement.

What is the price of VoopIX device?

VoopIX device is secured from the state budget, and its procurement and maintenance for the facility is completely free. No additional human involvement is expected from the institution (e.g. a CARNET system engineer).

Is there a violation of the law/contract with the telecom operator by using voopIX system?

This service is not a substitute for an existing telephone connection with a telecom operator, but an upgrade to an existing system. This is a private telephone network of CARNET member institutions, which is not subject to the Telecommunications Act, as it is not about providing public voice services.

How is it possible to check if the call is free?

On you can check if a particular phone number is in the category of free phone numbers. An electronic identity in the AAi @ EduHr system is required to access this page. As there is a possibility to change the category, an international call is made when the caller receives the toll-free message about the toll-free call.

Does one need to use special (pre)dialling when using voopIX?

On the side of the end-user, the service is completely transparent, i.e. the final user chooses the phone number as usual and is unaware of whether the call is passing through voopIX or through public voice network (JGM), but the entire logic of selection of the call locations termination is hidden.

What happens to phone connections when the connection to CARNET network is terminated? Do phone calls redirect automatically to classic phone lines or do you need to manually make redirects?

In case of disconnecting the CARNET connection, current calls going through the voopIX system (other members in the system) shall be interrupted, but not the current active phone calls to other users. Calls shall not be toll-free until you re-establish your connection to CARNET. In case of interruption, the conversations are automatically redirected to the public network and no additional human activity is required.

Are there any complaints from users about problems with voopIX conversations?

Occasional issues have arisen in some installations, but mostly initial problems at the very connection, but after the corresponding solution they have not appeared anymore.

Is there a longer wait to make a call or are there any other problems that may arise in operation?

As far as we know, there are no longer waiting times for making calls or no other issues.

Who maintains the device (card) used for voopIX in case of failure?

Everything related to voopIX is funded and maintained by CARNET.

What equipment will be included in the existing system to make VoopIX work?

The equipment depends on the existing installation at the facility, but it is usually a device built according to the CARNET specification.

Which protocols are used for connecting to the VoopIX Central at my facility?

The SIP and IAX2 protocols are used to connect to the voopIX switchboard. SCCP (Skinny Call Control Protocol or Skinny shortened) is not supported.

Local network has been installed in our facility. Do we have to cable in anything else?

Additional cabling is not always necessary. Most of today’s IP phones have at least two Ethernet ports and one connects directly to the network and the other one to the computer. In this case, it is desirable to have a network switch that has built-in support for VLANs to separate the phone from the rest of the network at a logical level. This shall avoid additional cabling costs due to telephony.

What network infrastructure should an institution have for connecting to voopIX?

In order for the VoopIX service to work without difficulty, the institution has to be a CARNET member and has to be connected to CARNET network by optics. The institution that is connected to aDSL technology cannot be connected to voopIX due to slower upload speeds, and it is also not possible to reserve part of VoIP traffic in order for voice-mail to flow smoothly. Prior to joining the voopIX, CARNet shall determine the current situation and propose an optimal solution, and if necessary maintain a system presentation to technical and non-technical staff.

Existing system users
What are Contexts when adding a new phone?

Context is an option that specifies the limitations of outgoing calls for each phone user.

5 contexts are defined:

  • local: enabled calls within the county (01, 042, 020 …)
  • international: enabled all calls including international
  • mobile phones: enabled calls within Croatia and calls to mobile networks
  • long distance: enabled all calls in Croatia except for mobile networks
  • pbx: enabled calls only to local telephones within the facility.
Is there a possibility of printouts of outgoing calls in CDR grouped by extensions?

Currently, this option does not exist.

Contact Details


Phone: +385 1 6661 555