My DSL/WiFi router lists the IPv6 GU- and LL- Address for each connected device, alongside the device's MAC address. When a device uses VPN, these addresses disappear from the LAN status listing.
Why is that? Is the VPN dropping to IPv4?
I am asking this, because the VPN circumvents the parental controls of the router, and this seems (so far) the only thing that changes when the VPN is on/off. And perhaps the router's controls are based on filtering based on the IPv6 LL address.
EDIT: to be clear, the parental controls are for time of day, not for specific websites. During restricted hours, say bedtime, the router blocks a device. Devices are recognized initially by their MAC address, that's how I, as admin, set restrictions for individual devices. It seems that the filtering/blocking itself after that is not based on MAC address but on something else.
I am going to see what the router's tech help can tell me, but I am not trouble shooting the router. I want to learn about the effectiveness of access restrictions. If it helps, the router is an Actiontec T3200 with broadcom inside (I believe), and the restricted device is an iPhone with VPN360 ("Unlimited Free VPN Proxy"). With the VPN off, the restrictions work.
The answer by Steffen Ullrich at My ISP provides IPv6 natively but my VPN does not support IPv6 is also illuminating.