Whilst transferring a site to ISPConfig3 via FTP and FileZilla I kept getting a disconnect with the error “Maximum number of connections from this IP (3) exceeded”. The default number of ftp connections in ISPConfig3, The Perfect Server, is 10. The default number of simultaneous ftp connections from one specific IP address is 3. To change these values you need to edit the Pure-ftpd configuration file. On my server this is /etc/pure-ftpd/pure-ftpd.conf. Edit the following lines with values suited to your application.
MaxClientsNumber 10
MaxClientsPerIP 3
