Description

This article is from the Firewalls FAQ, by Matt Curtin cmcurtin@interhack.net and Marcus J. Ranum mjr@nfr.com with numerous contributions by others.

61 What software uses what FTP mode? (Firewalls - TCP and UDP Ports)

It is up to the client to decide what mode to use; the default mode when a
new connection is opened is ``active mode''.

Most FTP clients come preconfigured to use active mode, but provide an
option to use ``passive'' (``PASV'') mode. An exception is the windows
command line FTP client which only operates in active mode.

Web Browsers generally use passive mode when connecting via FTP, with a
weird exception: MSIE 5 will use active FTP when FTP:ing in ``File
Explorer'' mode and passive FTP when FTP:ing in ``Web Page'' mode. There is
no reason whatsoever for this behaviour; my guess is that someone in Redmond
with no knowledge of FTP decided that ``Of course we'll use active mode when
we're in file explorer mode, since that looks more active than a web page''.
Go figure.

 

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security, Internet, firewalls, ssl, port, protection, application layer, proxy server, packet screening, filtering rules, viruses, terms