Using FTP, issuing the LIST command or attempting a file download or upload results in a timeout or error. In the Cerberus log file you will frequently see a timeout after the client issues a PASV command.
FTP connections use a secondary data connection for directory listings and file transfers. The FTP client will attempt to establish a new data connection every time a directory listing or file transfer is initiated. If the data connection cannot be established, an error occurs. This frequently happens with passive data connections and is the most common issue experienced by customers.
One of two approaches will normally fix this issue, depending on the type of router/firewall on your network.
- Solution 1: Make sure your router is forwarding passive data connection traffic to the server running Cerberus. See the following FAQ entry for the necessary steps: Allowing passive FTP traffic into your network
- Solution 2: If configuring your router to forward passive data traffic into your network didn't fix the problem then your router might not like the PASV address being given out by your server. See the following FAQ entry for the steps to configure Cerberus FTP server to give out your internal address for FTP passive requests: Configure Cerberus to use the internal LAN IP for passive requests