Brocade Communications Systems ICX 7250 series, Configuration Manual

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FIGURE 20 OSPF network containing an NSSA
This example shows two routing domains, a BGP domain and an OSPF domain. The ASBR inside the NSSA imports external routes
from BGP into the NSSA as type 7 LSAs, which the ASBR floods throughout the NSSA.
The ABR translates the type 7 LSAs into type 5 LSAs. If a summary-address is configured for the NSSA, the ABR also summarizes the
LSAs into an aggregate LSA before flooding the type 5 LSAs into the backbone.
Because the NSSA is partially stubby the ABR does not flood external LSAs from the backbone into the NSSA. To provide access to the
rest of the Autonomous System (AS), the ABR generates a default type 7 LSA into the NSSA.
Link state advertisements
Brocade devices support the following types of LSAs, which are described in RFC 2328 and 3101:
• Router link
• Network link
• Summary link
• Autonomous system summary link
• AS external link
• Not-So-Stubby Area (NSSA) external link
• Grace LSAs
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 area 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.
OSPFv2 areas
Brocade FastIron Layer 3 Routing Configuration Guide
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