This bug is due to a failure in handling router advertisments.
According to RFC 4861 (page 20) a _Cur Hop Limit_ set to 0 means, that the Hop Limit is unspecified. Ubuntu 15.04 takes this literally and sets HL to 0.
Fortunately my router provided the option to set this field to a manual value, altough i suppose this is not the case for most routers.
This bug is due to a failure in handling router advertisments.
According to RFC 4861 (page 20) a _Cur Hop Limit_ set to 0 means, that the Hop Limit is unspecified. Ubuntu 15.04 takes this literally and sets HL to 0.
Fortunately my router provided the option to set this field to a manual value, altough i suppose this is not the case for most routers.