Using a NETRC file provides an alternative to specifying a user ID and password when logging in.
The NETRC file contains a set of configuration statements consisting of the keywords MACHINE, LOGIN, and PASSWORD as follows:
MACHINE server_address LOGIN user_ID PASSWORD password
Location of NETRC file:
Clients using the NETRC file can log in by specifying only the FTP server's IP address or host name. The client locates the NETRC file and searches for a match of the MACHINE value to know which user ID and password to use on the login.
If the NETRC file identifies FTP servers by host name, but the client's login specifies an IP address, the client would have to resolve the IP address to a host name to find a match.
If you want the client to resolve all IP addresses to host names prior to searching the NETRC file, select "Yes, I use NETRC login files which need the host name."