Use /sbin/ifconfig
ou /sbin/ip a l
e procure por qualquer linha que comece com inet6
.
$ ip a l eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.5/24 brd 192.168.0.255 scope global eth0
inet6 fe00::000:00ff:febc:a0/64 scope link
valid_lft forever preferred_lft forever