The DNS tab only shows when dynamic DNS is enabled in the Domain tab. By setting up dynamic DNS your users can enter a fixed symbolic IP name (such as "yourname.DNS4Me.com") to connect to your FTP server, even if your IP address changes.
Serv-U will also take care of automatically adjusting the IP address reported back to FTP clients when they use the PASV command, which happens for passive mode data transfers. This will make life easier for you if your server is behind a firewall and your IP address is dynamic, i.e. it changes every so often, since you no longer have to update the address by hand in the domain’s Advanced settings tab.
Note:
For Serv-U to automatically update your passive mode IP passive mode transfers have to be allowed, and the "use IP" field on the domain’s Advanced settings tab has to be left blank.
Enter the symbolic IP name for your FTP server here, as reported by your dynamic DNS provider. This is the IP name you give to others so they can connect to your FTP server.
The IP address reported in this field is the current numerical Internet IP address. Regardless if the FTP server is behind a firewall or on a LAN, this will report the server IP address as seen from the Internet.
Tip
If your IP address changes regularly, or you do not have a fixed symbolic IP name, your life can be made much easier by signing up with a dynamic DNS provider. Not only will this take care of making Serv-U work even if the underlying server IP changes, it will also make it much easier for your friends to remember the address of your server. While there are many dynamic DNS providers there is one we especially recommend: DNS4Me. It is made by RhinoSoft, the same people that market Serv-U. DNS4Me is easy to use, gets the job done without undue complexity, and Serv-U has been tested with it. Give it a try!
http://www.DNS4Me.com/
