You want to configure an interface to work on an IPv6 network.
The IPv6 address configuration is very similar to that for IPv4:
 aviva@router1# set interfaces fe-0/0/3 unit 0 family inet6 address fec0:1:1:1::2/64
For an interface to operate on an IPv6 network, it needs an IPv6 address in the inet6 address family. To see that the IPv6 address has been set, look at the logical interface:
aviva@router1> show interfaces fe-0/0/3.0 brief Logical interface fe-0/0/3.0 Flags: SNMP-Traps Encapsulation: ENET2 inet6 fe80::205:85ff:fe02:a403/64 fec0:1:1:1::2/64
Router Configuration and File Management
Basic Router Security and Access Control
Routing Policy and Firewall Filters