Link state advertisements

Communication among areas is provided by means of link state advertisements (LSAs). The LSAs supported for each area type are as follows:

• Backbone (area 0) supports LSAs 1, 2, 3, 4, 5, and 7.
• Nonbackbone, supports LSAs 1, 2, 3, 4, and 5.
• Stub area supports LSAs 1, 2, and 3.
• Totally stubby area (TSA) supports LSAs 1 and 2, and also supports a single LSA 3 per ABR, advertising a default route.
• No so stubby area (NSSA) supports LSAs 1, 2, 3, and 7.