Re: Restricting FTP data connection port range?

From: Robert Miller (rmiller_at_SMUD.ORG)
Date: 11/10/05

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    Date:         Thu, 10 Nov 2005 09:27:34 -0800
To: aix-l@Princeton.EDU

    My suspicion is that it is a firewall, network, or FTP server config
    issue... unfortunately both our network folks and theirs seem to be
    convinced it's a client problem, so until I can prove otherwise it's my
    problem...

    --rm

    -----Original Message-----
    From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU]On Behalf Of
    Lamar Saxon
    Sent: Thursday, November 10, 2005 9:15 AM
    To: aix-l@Princeton.EDU
    Subject: Re: Restricting FTP data connection port range?

    Not sure how you are going to restrict the port range of the client
    since the connection is going to be made to any open port on the client.
    We have had this issue before and it was due to the way our firewall
    rules were configured. I don't think we ever came up with a way to lock
    / limit the socket connection back to the client.

    Is this what you are experiencing ? A firewall blocking the port range
    of the connection ?

    Just curious, thanks...
    Lamar

    -----Original Message-----
    From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
    Robert Miller
    Sent: Thursday, November 10, 2005 11:08 AM
    To: aix-l@Princeton.EDU
    Subject: Re: Restricting FTP data connection port range?

    Actually this problem is happening both in active and passive mode
    (forgot to put that in the original question). You can actually set the
    FTP client to passive mode when using it interactively, which is how I
    was testing, and they both failed the same way...

    --rm

    -----Original Message-----
    From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU]On Behalf Of
    Lamar Saxon
    Sent: Thursday, November 10, 2005 8:58 AM
    To: aix-l@Princeton.EDU
    Subject: Re: Restricting FTP data connection port range?

    Might look @ putting the client in passive mode. From the docs:

    passive Toggles passive mode for file transfers. When a file transfer
    command (such as get, mget, put, or mput) is invoked with passive mode
    off, the ftp server opens a data connection back to the client. In
    passive mode, the client opens data connections to the server when
    sending or receiving data.

    This should force the client to open the connection back to the server.
    Not sure this will eliminate the issue though since the connection will
    be made between ftp server and an open socket on the client.

    Lamar

    -----Original Message-----
    From: IBM AIX Discussion List [mailto:aix-l@Princeton.EDU] On Behalf Of
    Robert Miller
    Sent: Thursday, November 10, 2005 10:45 AM
    To: aix-l@Princeton.EDU
    Subject: Restricting FTP data connection port range?

    Folks,

    We've been having an odd problem connecting to an FTP server, and they
    have asked that I restrict the FTP data ports from the client end (our
    end).

    Specifically, we're getting "425 Can't open data connection" errors
    intermittently, and the only thing that seems to be consistent is that
    the problem occurs when port 65535 is used.

    Does anyone know a way of restricting FTP data traffic to specific ports
    with the regular, vanilla FTP client? We're using AIX 5.2 ML2.

    I have briefly looked at the "no" command, and it looks like it might be
    useful, but I'm wondering what other effects restricting the available
    ports might have.

    Hopefully someone has already had to do this and knows the right bits to
    twiddle :)

    --rm

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