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    FTP Server Configuration Overview

    To transfer files by the system’s FTP server, you must configure the FTP server and ensure that FTP client software is installed on the network host.

    Although you can transfer any type of file by FTP to the E Series router, the principal aim of this feature is to allow the transfer of system files to nonvolatile storage (NVS). You can transfer files by FTP to the user space. You can then install files from the user space onto the system using the copy command. It is not possible to access the system files directly through FTP operations.

    FTP sessions on the E Series router use the virtual terminal (vty) lines. The E Series router divides its vty resources between Telnet, SSH, and FTP services. Each FTP session requires one vty line. The FTP service uses the authentication method configured for the vty lines.

    Features

    The system supports the following FTP features:

    • Compliance with RFC 959—File Transfer Protocol (FTP) (October 1985)
    • FTP passive mode
    • Efficient NVS organization
    • User authentication by RADIUS or password checking

    FTP Passive Mode

    Normally, when a client connects to an FTP server, the client establishes the control channel with the server, and the server responds by opening a data channel to the client. However, when the FTP client and server are on opposite sides of a firewall that prohibits inbound FTP connections, the server cannot open a data channel to the client.

    FTP passive mode overcomes this connection limitation. In passive mode, the client opens a control channel to the server, tells the server it wants to operate in passive mode, and opens the data channel to the server. This method of establishing the FTP connection allows both the control channel and the data channel to pass through the firewall in the allowed direction.

    Published: 2014-08-12