SIP Provider Deutsche Telekom, SIP Trunk and SIP Trunk Pure (DE) (kb4856)

The information in this article applies to:

  • SwyxWare 11
  • SwyxWare 2015

[ Summary | Information | Links ]


Information und configuration hints for SIP provider Deutsche Telekom, SIP Trunk and SIP Trunk Pure (Germany).


General information

The information published here applies both to the SIP Trunk standard, which is dependant from the Internet connection of Deutsche Telekom, and to the SIP Trunk Pure.

The SIP Trunk of Deutsche Telekom was first tested and released with a SwyxWare 2015 R3.5.

Deutsche Telekom is offering a SIP trunk with user authentication. You have received information about UserID, UserName and UserPassword, whereas the naming may differ, or you might have only received UserName and -password. In this case, UserID and UserName are identical. 


The SIP trunk of Deutsche Telekom can be used without restrictions from SwyxWare 2015 R3.5. When using an earlier version of SwyxWare incompatibilities cannot be excluded and use is at your own risk. However, the standard SIP trunk is linked to Deutsche Telekom's Internet connection, whereas the SIP trunk pure can be operated on any Internet connection.

Due to the dependence on the connection with standard SIP trunk or due to further technical restrictions, the connection to the SIP trunk pure must also be made locally at the customer via a suitable gateway. Configuration instructions for a LANCOM gateway are available for download at the end of the KB article.


During creation of the SIP Trunkgroup, profile 'Telekom Trunk TCP (DE)' must be selected.
If encryption is required, profile 'Telekom Trunk TLS (DE)' must be selected. It is mandatory to import two Telekom certificates into the Windows-Certificate store of the SwyxWare server.

UPDATE: Since both mentioned certificates will expire in June 2019, it is necessary to install a different certificate until 25th of April 2019. Additional information (in German) can be found as download link at the end of this article.

Required information:

  • Access number (previously T-Online Number) or Telephony-Username, i.e. 11223344
  • Personal password for the Telekom SIP Trunk
  • assigned number range, i.e. +49 401122330 - +49 4011223339

This information is provided by Deutsche Telekom when the connection is created or can be accessed through the Telekom customer center.

As UserId for the created SIP Trunk, the first number of the available number range has to be configured, i.e. +49401122330. User name is the Access number (previously T-Online Number) or Telephony-Username respectively.

In the codec dialog, G.711u and G.729 can be deselected, T.38 as supported codec must be deselected.

FAX transmission

The Telekom SIP Trunk does not support the T.38 protocol, which is strongly recommended for FAX transmission in an IP environment. The alternative method for FAX transmission via G.711 is supported from SwyxWare2015R3 on. In oder to prevent the intended T.38 stream switch, it is necessary to remove the T.38 codec from the list of supported codecs.

Note: Quality and reliability of a FAX transmission via G.711 strongly depends on the end-to-end network connection. Since the control and redundancy information from the T.38 protocol are missing, especially the transmission of larger documents may fail.

Tested Features

  • Incoming/outgoing national calls
  • Incoming/outgoing international calls
  • Correct Calling Line Identificaion (CLI) on national and international calls
  • CLIP No Screening
  • Holding and retrieving calls
  • Toggeling between two calls
  • Call transfer
  • Call forwarding
  • Conferencing
  • Mutually supported codecs:
    • G.722
    • G.711a
  • Incoming/outgoing DTMF signaling in accordance with via RFC2833
  • FAX transmission via G.711

Test dates:
02/09/2016 with SwyxWare2015R30.5
14/03/2018 with SwyxWare

Overview of tested SIP provider


As far as software supplied or used by us, includes open source elements the additional terms under apply in addition. An overview which products from the Swyx portfolio include open source elements and which open source license is relevant can be found under

The third-party contact information included in this article is provided to help you find the technical support you need. This contact information is subject to change without notice. Swyx in no way guarantees the accuracy of this third-party contact information nor is responsible for it's content.


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