FTP client: Sends a request to open a command channel from its TCP port 6000 to the FTP server’s TCP port 21.

(For the purposes of this example, we’ll assume ports TCP 6000 and TCP 6001.)

FTP client: Opens random response ports in the high number range.

The sequence of events for a PORT FTP connection goes like this: The traditional FTP mode is referred to as PORT (or Normal or Active ) mode FTP.

Let’s look at these two modes in more detail. PORT mode (also known as Normal or Active mode) How your clients and servers make these connections depends on the FTP mode. In this article, we’ll look at the following issues:įTP is a messy protocol because it requires multiple connections, sometimes in both directions. If these administrators understood how FTP worked and how typical firewalls augment the protocol’s sometimes dicey security demands, they would be able to easily solve the FTP-related problems they encounter. I get many questions every day from router and firewall administrators asking why a particular FTP client or server configuration isn’t working. The File Transfer Protocol (FTP) is one of the most popular, but also most misunderstood, protocols in use today.

The problem is, FTP is a messy protocol that needs a lot of help to secure it. Nearly everyone uses FTP for one reason or another. How FTP port requests challenge firewall security

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