FRITZ!Box 3370 Service - Knowledge Base

FRITZ!Box 3370 Service

Error message "The port sharing cannot be created or enabled [...]".

You cannot set up port sharing in the FRITZ!Box. When you try to create a port sharing, one of the following error messages is displayed:

  • "Port sharing cannot be configured or enabled, because there is already a corresponding port sharing setting."
  • "Port sharing cannot be configured or enabled because the rules conflict with an internal rule."
  • "Port sharing cannot be created or enabled, because the port is already in use for remote maintenance (HTTPS) (Internet / Permit Access / FRITZ!Box Services)."
  • "Port sharing cannot be created or enabled because Internet access to your storage media over FTP/FTPS is enabled (Internet / Permit Access / FRITZ!Box Services)."


  • You are trying to create a second port sharing rule for a TCP or UDP port, or for the IP protocols ESP or GRE in the FRITZ!Box. However, as a rule it is not possible to configure multiple port sharing rules for the same port or for the IP protocols ESP or GRE in a network router like the FRITZ!Box.

    Note:The FRITZ!Box checks all incoming and outgoing data packets and automatically rejects unrequested data from the Internet (Stateful Packet Inspection). The FRITZ!Box uses the NAT (Network Address Translation) mechanism to check incoming data and determine which port it is addressed to, which IP protocol it is transporting, and which device it should be forwarded to. If ports or IP protocols are shared more than once, it is no longer clear which device the data is intended for. Therefore, it is not possible to configure multiple port sharing rules with NAT.

1 Ports used by the FRITZ!Box

The FRITZ!Box itself uses some ports to provide functions such as Internet telephony. Here we give you an overview of ports that are typically opened by FRITZ!Box services:

Note:You can find a list of all the ports being used by your FRITZ!Box in the user interface under "Diagnostics > Security".

  • TCP port 21 (Internet access to storage media via FTP/FTPS)
  • TCP port 443 (MyFRITZ! or Internet access to the user interface via HTTPS)
  • UDP ports 500 and 4500 (VPN)
  • TCP and UDP port 5060 (Internet telephony)
  • UDP ports 7078-7109 (Internet telephony)
  • TCP port 8089 (automatic configuration over TR-069)

2 Using a different port

If Internet applications (for example chat software or online games) or several computers, game consoles or other network devices connected to the FRITZ!Box require the same TCP or UDP port for incoming connections from the Internet, configure the devices or applications so that they all use different ports:

Important:IP protocols ESP and GRE can only be shared for one device. There is no workaround for these IP protocols.

  1. Configure the device or Internet application so that ports not used by the FRITZ!Box, other devices, or other Internet applications accept connections from the Internet.

    Important:If you use the same application on several computers, assign different ports for incoming connections in the application on each computer.

  2. Set up port sharings in the FRITZ!Box for the new ports you configured in the device or the Internet application.

Now all of the devices or Internet applications for which you configured port sharing can accept connections from the Internet.