Exam JN0-648 topic 1 question 56 discussion

https://www.juniper.net/documentation/en_US/junos/topics/example/example-configuring-is-is-route-leaking-L2-to-L1.html "By default, IS-IS protocol leaks routing information from a Level 1 area to a Level 2 area. However, to leak routing information from a Level 2 area to a Level 1 area, an export policy must be explicitly configured." https://www.juniper.net/documentation/en_US/junos/topics/example/isis-multi-level.html "An IS-IS Level 2 area is analogous to the OSPF backbone area (0), while a Level 1 area operates much like an OSPF totally stubby area, in that a default route is normally used to reach both inter-level and AS external routes."