[HOWTO] Configure IPv6 in order to "just work" (tm)

[Maurice]

The "track interface" feature for NPT uses the prefix which is on-link on the selected interface. When using NPT for Internet access, this will typically be the WAN interface. This has several disadvantages; most importantly, you can only use NPT for a single LAN subnet.

What would make more sense is using a subnet of the delegated prefix (like it's done for "track interface" type LAN interfaces), but that's currently not supported.