A Level 1-2 router has two IS-IS databases. The Level 1 database is used for routing to destinations within the router's configured area. The Level 2 database is used to route between destinations in different areas.
An Area Border Router (ABR).
By default, all routes are advertised into all OSPF areas. This includes interarea OSPF routes and external routes that have been injected into OSPF. By default, IS-IS does not advertise interarea or external routes into an area, but injects a default route.
Redistribution of Level 2 routes into an area as Level 1 routes.
An OSPF interface metric is determined from the interface bandwidth. By default, all IS-IS interface metrics are equal to 10.