MS ISA Server 2006 and FTP
Posted by dgcom on June 16, 2007
Technorati tags: computers
Technorati tags: computers
After upgrading ISA server to 2006 version, I was surprised to find that my FTP behind it stopped working in passive mode. Having quite smart FTP server installed I blamed MS ISA for this and did not have time to look at this deeper… until I found a need for this - had to move my Blogger blog from 1and1 hosting (expired free one) to my own server. And Blogger refused to publish the blog unless I have passive FTP working.
FTP client was getting 500 response – that FTP server sent bad response. Quick capture on ISA server showed that my FTP server was too smart – it actually was configured to return correct IP address in PORT command (the external IP, not default internal one). This, turns out, is “bad” thing from ISA server FTP filter prospective. Turning advanced NAT support on FTP server, making him return internal IP, fixed this – now ISA server could replace that IP with the external one it knows about.
But that got me thinking – software gets smarter, you try make it better and as end result – there is some stupid “simplification” (or “assumption”) made by other developer broke functionality.
Granted, if I’d read the docs for ISA server, I might have caught this, but sorry, RTFM is the last thing I’d do. 
