FRITZ!Box 7340 – Service - Knowledge Base

FRITZ!Box 7340 – Service
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FRITZ!Box reports "ERROR: Entry already exists" when setting up port sharing

It is not possible to set up port sharing for identical TCP or UDP ports or for the IP protocols ESP and GRE in the FRITZ!Box. When attempting to set up port sharing, the error message "ERROR: Entry already exists" is displayed.

1 Cannot share the same port or IP protocol more than once

Only one port sharing rule can be configured in the FRITZ!Box for each TCP or UDP port, or the IP protocols ESP and GRE. As a rule, it is not possible to configure several port sharing rules for the same port or the IP protocols ESP and GRE in network routers such as the FRITZ!Box.

Note:The FRITZ!Box checks all incoming and outgoing data packets and automatically rejects unwanted 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.

Workaround

If Internet applications (for example chat software or online games) or several computers, game consoles or other 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 application so that it does not use the same ports to accept connections from the Internet that are used by the FRITZ!Box, other devices, or other applications.

    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 application.

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