As of 20150917T235937Z IPv6 support has been added to vmadm via a new property "ips". The ips parameter supports multiple addresses including IPv4, IPv6, dhcp (for IPv4), and addrconf (for SLAAC or DHCPv6).
Link local addresses, DHCPv6 and static are implicitly permitted. As of 20151224T060557Z, SLAAC addresses are, too. Before that, though, each SLAAC address needs to be added to nics.*.allowed_ips or allow_ip_spoofing needs to be enabled. If an IPv6 address or addrconf are specified, in.ndpd will be automatically enabled.
In this example, the expected IPv6 address has been derived from the "mac" field via EUI-64 and added to "allowed_ips".
See vmadm(1) for more information.