IPv6 is the name of the networking protocol which is rapidly replacing the use of IPv4 in wake of widespread IPv4 exhaustion.  IPv6 is defined in 1998’s RFC 2460.

IPv6 addresses are written in “colon notation” like “fe80:1343:4143:5642:6356:3452:5343:01a4” rather than the “dot notation” used by IPv4 addresses such as ”″.  IPv6 DNS entries are handled through “AAAA” entries rather than “A” entries under IPv4.

BEST PRACTICES: All FTP technology should now support an RFC 2428 implementation of IPv6 and the EPSV (and EPRT) commands under both IPv4 and IPv6.  Until IPv4 is entirely retired, the use of technology that supports both IPv4 and IPv6 implementations of FTP is preferred. Avoid using FTP over connections that automatically switch from IPv6 to IPv4 or visa versa.