I think ipv6 pass through means there is a bridge between the wan and the single lan. Click status to check whether you have successfully set up an ipv6 connection.

How To Set Up An Ipv6 Internet Connection On The Wi Fi
What is ipv6 passthrough. For this tutorial i will choose the native as my preferred ipv6 connection type. Ipv6 will eventually replace ipv4. If no address is acquired the field displays not available. All ipv6 traffic over wifi is blocked and doesnt even reach the ea7500 router. Ipv6 increases the ip address size from 32 bits to 128 bits to support more levels of addressing hierarchy. Pas through seemed to work as it effectively also disabled ipv6.
The transition from ipv4 to ipv6 that is currently underway creates a big problem for most vpn services. Click save and skip to step 6. Fill in address prefix provided by your isp and click save. If pass through is needed for working ipv6 then i would say the isp has done something wrong. Windows users are recommended to choose from the first two types. The following figure is an example of a successful pppoe.
Ok i discoverred that pass through actually does not work either and the issue is actually an ipv6 bug. Ipv4 is the current industry standard in tcpip networks today and is the de facto internet routing protocol. Wan automatic ip select passthrough as ipv6 connection type wan static ip select static static ipv6 as ipv6 connection type native profile was selected. The number after the slash is the length of the prefix which is also indicated by the underline under the ipv6 address. My understanding is that passthrough means that the router does not look at the ipv6 header and operates as a l2 switch where it simply forwards the packet. Routers ipv6 address on wan.
Asus has both an ipv4 and ipv6 firewall that is enabled by default. All ipv6 traffic over wired ethernet works fine. Of course upgrading servers to support ipv6 is an expensive and difficult fix. Most vpns have been slow to accommodate this transition to ipv6 and update their server networks. With ipv6 the customer should get a routed prefix 48 52 56 60 or 64 for example using dhcpv6 pd which doesnt require pass through or bridging. This field shows the ipv6 address that is acquired for the routers wan or internet interface.