Which statement describes the default Junos OS behavior for OSPF?

A.
External LSAs are advertised in a stub area.

B.
An ABR does not announce a default route into a stub area.

C.
Stub area internal routers generate a default route.

D.
Only totally stubby areas need a default route.

Explanation:
Stub areas are areas through which or into which AS external advertisements are not flooded. You might want to create stub areas when much of the topological database consists of AS external advertisements. Doing so reduces the size of the topological databases and therefore the amount of memory required on the internal routers in the stub area.

Routing devices within a stub area rely on the default routes originated by the areas ABR to reach external AS destinations. You must configure the default-metric option on the ABR before it advertises a default route. Once configured, the ABR advertises a default route in place of the external routes that are not being advertised within the stub area, so that routing devices in the stub area can reach destinations outside the area.

The following restrictions apply to stub areas: you cannot create a virtual link through a stub area, a stub area cannot contain an AS boundary router, the backbone cannot be a stub area, and you cannot configure an area as both a stub area and a not-so-stubby area.