NE40 is a level1-2 router, and NE08 is level1 one. NE08 is required to generate one default route to NE40 automatically. However, the default route cannot be found on NE08 in the topology.
Level1-2 router needs to receive the routes of Level2 at outside, and then it could distribute a default route to level1 router.
According to ISIS, level1-2 router is to adverise a default route to level1 router. However, level1 router does not generate a default route in the case, which is because that level1-2 router does not receive the level2 routing entries created by others, so level1-2 router will not advertise a default route to level1 router.