What is ACL ?
When you enable it , only selected ips have access to FTP server as a client. it is for security of FTP. if some one stole your FTP.
How to ? It is depends on your FTP provider. But if you have own linux server.
access-list 101 permit tcp any any eq 21
!--- The above line permits TCP traffic from any source, such as the FTP client,
!--- FTP server destination at the FTP control port 21.
access-list 101 permit tcp any eq 20 any
!--- The above line permits TCP traffic from any source, such as the FTP server,
!--- FTP client at FTP data port 20.
Example Document :
NFS Sun’s Network Filesystem (NFS) is the preferred method of file sharing for networks of Unix or Linux computers. The Linux kernel includes both NFS client support
Coda This is an advanced network filesystem that supports features omitted from NFS. These features include better security (including encryption) and improved caching.
SMB/CIFS The Server Message Block (SMB) protocol, which has been renamed the Core Internet Filesystem (CIFS), is the usual means of network file sharing among Microsoft OSs. The Linux kernel includes SMB/CIFS client support, so you can mount SMB/CIFS shares. You can configure your Linux computer as an SMB/CIFS server using the Samba package (http://www.samba.org). The filesystem type code for SMB/CIFS shares is smbfs.
NCP The NetWare Core Protocol (NCP) is NetWare’s file sharing protocol. As with SMB/CIFS, Linux includes basic NCP client support in the kernel, and you can add separate server packages to turn Linux into an NCP server. NCP’s filesystem type code is ncpfs.