To manually assign an IP address for an interface, edit the
file /etc/sysconfig/network-scripts/ifcfg-interface. Add or correct the
following line (substituting the correct IPv6 address):
IPV6ADDR=2001:0DB8::ABCD/64
Manually assigning an IP address is preferable to accepting one from routers or
from the network otherwise. The example address here is an IPv6 address
reserved for documentation purposes, as defined by RFC3849.