netstat: no support for AF INET6 .. 무슨 메시지인가요?

netstat -na
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN
tcp        0      0 0.0.0.0:23              0.0.0.0:*               LISTEN
netstat: no support for 'AF INET6 (tcp)' on this system
udp        0      0 0.0.0.0:111             0.0.0.0:*
netstat: no support for 'AF INET6 (udp)' on this system
netstat: no support for 'AF INET6 (raw)' on this system
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags       Type       State         I-Node Path
unix  2      [ ]         DGRAM                    494    @/org/kernel/udev/udevd