Which three statements are true regarding the IS-IS link-state database (LSDB)? (Choose
three.)
A.
Route leaking can be used to optimize Level 2 to Level 1 routing.
B.
An attached router has at least two LSDBs: one for each Level 1 area and a single LSDB
for the Level 2 backbone.
C.
The Level 2 database contains only backbone area routes unless route leaking is
configured.
D.
An L1 router often relies on a default route generated by attached routers to reach
interarea destinations.
E.
An L1 router has a single database reflecting the connectivity of its area.
Explanation:
D.
An L1 router often relies on a default route generated by attached routers to reach
interarea destinations.
-actually no default route is advertised by the attached router instead the L1 router will generate and install a default route in its routing table upon receipt of the LSP with ATT bit set and the default route is pointing to the originator of the LSP.