To configure IPv6 on an ASUS RT-N66U router, log in and enter the IPv6 setup page by selecting ‘Advanced Settings’ > ‘IPv6’.

Configure the settings on this page per the the following:

Connection type: Native
Interface: PPP
DHCP-PD: Enable
Accept Default Route: Enable
Auto Configuration Setting: Stateless
Connect to DNS Server Automatically: Enable
Enable Router Advertisement: Enable