Re: [MLUG - DISCUSSION] FTP error

[Mikhail Kovalenko <EMAIL:PROTECTED>]

Ross, Matt wrote:

> Now, several organizations can't click to the files from within their LAN,
> though one was able to click to the files from his firewall box.  We sent
> one person to check from home using Compuserve dialup, and he couldn't click
> to it.  These people can type in the ftp address and go to the folder, but
> clicking doesn't work.  Most are using internet exploder, but a few we don't
> know what they're using.  All are using windows.  In the log file, these
> show up as connection failed, and account for 9% of the attempts.  Most
> attempts from AOL come through just fine, as are most using IE.  Any clue
> why this 9% can't click their way in?

My guess is that their firewalls are not allowing active-mode FTP to 
take place. IIRC, when you request an FTP file in active mode, the FTP 
server will try to make a data connection back to your computer (from/to 
port 20, I believe). If a NAT firewall doesn't account for it, all data 
connections back to requesting machine will fail since they will appear 
as unrelated connections from the outside. That would only happen on a 
NATed connection and should not affect the firewall machine itself since 
then it would be the request originator.

With active mode disabled, the data gets transmitted within the same 
session back to your computer. I seem to recall a checkbox in IE under 
Advanced Options that should take care of that ("Use Web Based FTP", 
maybe?).

Cheers,
MK

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