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Knowledge document #907

Application (e.g. SSH) occasionally loses its connection to remote sites on the internet

The internet connection of a single application is cleared after about 15 minutes, although you can open web pages on the same computer at the time the error occurred. This issue occurs with SSH (Secure Shell) or Telnet connections to remote sites on the internet, for example.

Cause

  • To guarantee the security of devices in the FRITZ!Box home network and avoid internet performance issues, if no data is exchanged across a TCP connection for 15 minutes, or no data is exchanged across a UDP connection for 5 minutes, the FRITZ!Box automatically deletes the respective connection(s) from its NAT table ("NAT Timeout"). This means that all of the ports that were used by these connections are closed and the internet connection of the corresponding application is cleared.

Enabling the keepalive function in the application

  1. To prevent the FRITZ!Box from deleting connection information from its NAT table, configure the internet application so that it sends data packets to the internet at regular intervals.

    Note:This is usually called the keepalive function. Refer to the manufacturer for information on how to set it up, for example consult the manual.

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