The Foundation Summary provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary might help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final prep before the exam, the following lists and tables are a convenient way to review the day before the exam.
There are three special types of OSPF areas:
Stub— A stub area ABR only injects interarea LSAs and a default route into the area.
Totally Stubby— A totally stubby area ABR only injects a default route into the area. The totally stubby option is Cisco proprietary.
NSSA— An NSSA provides a mechanism for ASBRs attached to a (non-backbone) stub area to propagate external routes (via type 7 LSAs) into the routing domain.
The following authentication options are available for securing the OSPF configuration:
The most useful commands for verifying and troubleshooting OSPF configurations related to the three specialized OSPF areas and OSPF authentication are
show ip ospf neighbor
show ip ospf interface
debug ip ospf adjacency