FTP Error 421

[EzehM]

Our FTP server (running IIS 6.0) seems to be returning FTP error 421 to connected users on a weekly basis. We have about 60 clients that connect to this server at random times during the day.

The error temporarily disappears when we reboot the FTP server. Does anyone know what the cause of this problem could be?

Thanks

 

[WhoKilledKenny]

Just from what you described I would look at the properties of the FTP Site and look at the number of connections you are allowing. You may be reaching your connection limit and by re-booting the server you resolve the issue as it disconnects the current users. There is also a "Current Sessions" button that will show you who is currently accessing your ftp site and how long they have been connectted.

 

[WhoKilledKenny]

Also, what OS version are you running? I am assuming you are running on a Windows server platform, but if you are running a workstation platform (XP, Win2000Pro) you are limited to 10 Connections.

 

[EzehM]

WhoKilledKenny, thanks for your response.

OS: Windows 2003 Server.

I also set FTP Site Connections to Unlimited. At any given time the number of concurrent users is never more than 3.

Any ideas?

 

[WhoKilledKenny]

There could be a number of reasons why you are seeing this error. Most of what I am seeing on the Internet is that 421 is a temporary error. Are you re-booting the server just to clear the errors or are you re-booting because no one is able to connect?

Some of the reasons I've seen:
Multiple connections to the FTP server by the same user account.
Windows Firewall know to cause error code.

 

[monksnake]

Take a look at this site EzehM, this shows a list of FTP errors and gives you things you can do to fix them (or at least diagnose them)

http://kb.globalscape.com/article.aspx?id=10142

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[EzehM]

WhokilledKenny - I have to reboot the server because no-one else can connect once these errors start. I am looking into the case of multiple connections from one IP but the FTP log isnt really helpful.

monksnake - Thanks for the link.

I just wonder whether setting a limited number of allowed connections will get rid of this problem (i.e. not stopping everyone else from connecting once this error starts).