To avoid having too much client to client traffic on your network you can use 'ipv6 nd prefix default ... off-link', don't forget to also add a route towards the interface on the router itself so:
interface GigabitEthernet0/0/0
ipv6 address 2001:0db8:5150:F016::1/64
ipv6 enable
ipv6 nd reachable-time 600000
ipv6 nd prefix default infinite infinite off-link
ipv6 nd other-config-flag
ipv6 nd router-preference High
ipv6 nd ra lifetime 9000
ipv6 nd ra dns server ...
ipv6 dhcp server ...
ipv6 verify unicast source reachable-via rx allow-default
...
ipv6 route 2001:0db8:5150:F016::/64 GigabitEthernet0/0/0
(this is a configuration optimized for wireless networks with very long timers)
This means that the client gets a default route, but no route towards the /64:
Internet6:
Destination Gateway Flags Netif Expire
default fe80::72ca:9bff:fe88:da83%en0 UGc en0
::1 ::1 UHL lo0
...
And your client will only see the router as neighbour:
$ ndp -a -n
Neighbor Linklayer Address Netif Expire St Flgs Prbs
...
fe80::72ca:9bff:fe88:da83%en0 70:ca:9b:88:da:83 en0 23h59m57s S R
So all the client to client traffic in the /64 will work, but will go via the router.
