FTP passive or active

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Oct 24th, 2007
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Hi all. I have an issue where a 1750 using IOS 12.1.3(XT2). I have client software on the LAN side that creates an FTP connection, authenticates, then disconnects without transferring any files.

I called the company and they stated that it could be an ftp "active/passive" issue. Can anyone shed any light on why I would need to make adjustments to my config?

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a.cruea1980 Wed, 10/24/2007 - 13:54
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Because active FTP connections use a random port for data transfer, but passive uses port 20, if I remember correctly.

It would probably be wiser to make the clients use passive FTP than to change your router around to try and get connections through.

Frank Hoeben Thu, 10/25/2007 - 05:12
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You've got it the wrong way around.

PASV uses a random >1024 port, while non-passive uses port 20 for data connections.

BOTH can be a pain to setup if the FTP server is unaware of being behind NAT.

slayerhawk Tue, 11/06/2007 - 14:26
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Has anyone made this work? The clients on the LAN side use an active ftp session. I have used an access list that allows all tcp, ip, and udp to the host ip address.


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