Hello Network Experts (I hope),

For all but one of the web site hosting companies I use I can download large files OK using an FTP client such as Filezilla.

However for one hosting company: Upload works fine via ftp client. Download of files smaller than about 3MB works fine via ftp client. Download of files of 3MB or larger works individually via browser i.e. via ftp://....... Download of files of 3MB or larger via Filezilla (or Windows Explorer or FireFTP) fails with a timeout after about 20 seconds.

The hosting company has been unable to solve the problem so far. They say they have removed the timeout limit, but I still have the same problem.

According to the Filezilla documentation this could be due to a faulty firewall or router. http://wiki.filezilla-project.org/Network_Configuration#Timeouts_on_large_files I am not a network expert however if it is working OK for other hosting companies (which also run IIS6) then I assume my firewall and router must be OK.

I would prefer to use an FTP client as then I should be able to FTP download the whole site in one go.

Any idea what could be the fault or if it is a firewall or router how to find out which piece of equipment is faulty?



  • This smells like a PMTU black hole issue. Maybe some clueless person blocked ICMP. – David Schwartz Mar 20 '17 at 22:14
  • Did you test your internet connection to make sure its not interrupted, so you tcp connection is being disconnected? in these cases the FTP client will reconnect and continue the download prosess - if the server support this. In this case it can work on multiple ftp servers, but fails on other if they dont support reconnection. – Mr Zach Nov 12 '17 at 9:02

There should not be a reason why a browser download works file a FTP client download does not work unless there is something wrong. A couple of things to check.

  1. Whether your FTP client is configured to use PASSIVE ftp mode or not. Try changing it to see if it works. This might be a problem since the two modes use different ftp ports, which may be subject to different firewall rules.
  2. Whether your browser is quietly resuming any broken downloads in the background.
  • 1. Filezilla wa previously set to "default" which used passive for this connection. So I tried changing it to active but then it gave Response: 230 User logged in, proceed. Status: Connected Status: Retrieving directory listing... Command: PWD Response: 257 "/" is current directory. Command: TYPE I Response: 200 Type set to I. Command: PORT 78,189,189,73,197,110 Response: 200 PORT Command successful. Command: LIST Response: 150 Opening ASCII mode data connection for /bin/ls. Error: Connection timed out Error: Failed to retrieve directory listing – user63086 Dec 10 '10 at 7:42
  • 2) Not sure how to check whether browsers (FF and IE) are resuming however they are pretty quick so seems unlikely. However Filezilla makes 3 attempts and fails each time and FireFTP keeps on trying until I cancel it. – user63086 Dec 10 '10 at 7:52
  • @user63086 that looks like you are behind a firewall that is not forwarding the connection to you when the server tries to establish the data connection. Using passive mode gets around this problem by having your computer connect to the server instead of the other way around. – psusi Jul 12 '11 at 15:19

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