Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) - Manual (Page 125)

Brocade Virtual ADX Switch and Router Guide 111
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Configuring OSPF
6
NOTE
You can assign one area on a router interface. For example, if the system or chassis module has 16
ports, 16 areas are supported on the chassis or module.
Assign a Not-So-Stubby Area (NSSA)
The OSPF Not So Stubby Area (NSSA) feature enables you to configure OSPF areas that provide the
benefits of stub areas, but that also are capable of importing external route information. OSPF
does not flood external routes from other areas into an NSSA, but does translate and flood route
information from the NSSA into other areas such as the backbone.
NSSAs are especially useful when you want to summarize Type-5 External LSAs (external routes)
before forwarding them into an OSPF area. The OSPF specification (RFC 2328) prohibits
summarization of Type-5 LSAs and requires OSPF to flood Type-5 LSAs throughout a routing
domain. When you configure an NSSA, you can specify an address range for aggregating the
external routes that the NSSA's ABR exports into other areas.
The Brocade implementation of NSSA is based on RFC 1587.
Figure 23 shows an example of an OSPF network containing an NSSA.
FIGURE 23 OSPF network containing an NSSA
This example shows two routing domains, a RIP domain and an OSPF domain. The ASBR inside the
NSSA imports external routes from RIP into the NSSA as Type-7 LSAs, which the ASBR floods
throughout the NSSA.