In case of IPv6, even if the users have public IPv6 address and is in the same network, traffic does not leave the network. So if you are sharing the same LAN,

In case of IPv6, even if the users have public IPv6 address and is in the same network, traffic does not leave the network. So if you are sharing the same LAN, it does not need internet. This is because the large IP address space make routing efficient, without the use of NAT.