FTP server accessible from the intranet only
Facts - Other software technologies
Wednesday, 13 October 2010 20:37

I was working on a windows pc with internet from a UMTS connection through a USB modem. In addition the PC was connected to a small intranet. So this PC had two IP addresses. The first IP address was provided by a DHCP server on the local intranet. The other IP address was provided via the USB mobile internet modem.

For security reasons I had to install an FTP server that was accessible from the intranet but not from the internet. I could have installed the FTP server on another PC on the intranet, but these were all laptops and therefore not connected all the time. So what I did was installing the FileZilla FTP server on this PC. That FTP server provides the possibility of specifying a specific IP address the FTP server has to bind to.

After logging in into the Administrative Interface in the FileZilla server I specified the local intranet IP address of my PC, this was 192.168.30.2. Specifying the IP address could be done by choosing Edit, Settings, IP bindings and then entering the IP address. The default value was "*", which means that the server has to bind to all available IP addresses. To see if the restriction on the IP address worked I ftp-ed to the IP address 192.168.30.2. This went well. Then I tried to ftp to the external FTP address, from the USB modem. As expected I got an error message Connection refused.