Update: I rebooted the device and it now shows just one uplink IPv6 prefix.
It looks like this: 2003:c1:XXXX:XXXX:XXXX:XXXX:XXXX:35b8/64. I also noticed something else. The IPv6-Page on the wiki states that:
If the router can
ping6the internet, but lan machines get “Destination unreachable: Unknown code 5” or “Source address failed ingress/egress policy” then the ip6assign option is missing on your lan interface.
So I had a look at the interface configuration:
config interface 'lan'
option proto 'static'
option ifname 'eth0.7'
option type 'bridge'
option ipaddr '10.0.0.1'
option netmask '255.255.255.0'
option ip6assign 64
option ip6hint ffff
So to me it seems like if (off course) can not assign prefixes with a length of /64 to the lan devices as the uplink only got one /64 prefix assigned. My first try was setting ip6assign to something larger (respectively a smaller net) like /90 but that seems not accepted.
So I am still stuck with the issue. Any ideas?