Hello Mephi,
I think you are missing the prefix part for the GUA on the eth2 interface, without that your are indeed overwriting the GUA.
give this a try:
set interface ethernet eth2 ipv6 router-advert prefix ::/64 autonomous-flag true set interface ethernet eth2 ipv6 router-advert prefix ::/64 on-link-flag true set interface ethernet eth2 ipv6 router-advert prefix ::/64 valid-lifetime 2592000
if you want to add an internal DNS Server
set interface ethernet eth2 ipv6 router-advert radvd-options "RDNSS fdee:eeee:eeee:0::53 {};"hope this helps :-)