If it's anything like the Rogers Hitron modems, a single /64 will be provided by default, along with a crappy firewall. What many do is put the modem into bridge mode and then connect to a router that supports DHCPv6-PD, which is used to assign the prefix to the router. On Rogers, the size of the prefix is user selectable, up to a /56, which provided 256 /64s. Each /64 can be assigned to an interface or VLAN as required.
I use pfSense
, but many consumer routers now support DHCPv6-PD, as do the WRT routers. I currently have 3 /64s configured. ! for my LAN, 1 for a test LAN and 1 for my OpenVPN clients. Incidentally, a /64 provides for 18.4 billion, billion addresses.
I haven't lost my mind. It's around here...somewhere...