On Jan 7, 2015, at 9:03 PM, Johnny Billquist <bqt at softjar.se> wrote: Thanks. (I doubt the VMS ftp server would care about NAT, it's not something the system behind a NAT knows or should care about. It's the NAT router who have to do all the work ) Usually, but it depends on the protocol. Some protocols FTP is a notorious example carry addresses and/or port numbers inside the application protocol data. Does this server support passive mode? A lot of NAT servers need passive mode for FTP to work, or work more reliably if you use passive mode. (I just like passive mode because it isn t quite so conceptually broken as the older mode of FTP.) paul