System information

BSR 64000 Configuration and Management Guide
11-8
Configuring OSPF Not So Stubby Area
The Not So Stubby Area (NSSA) is similar to the OSPF stub area. The BSR does not
flood Type 5 external LSAs from the backbone into the NSSA area, but it can import
AS external routes in a limited fashion within the area. NSSA allows importing of
Type 7 AS external routes within NSSA area by redistribution. These Type 7 LSAs
are translated into Type 5 LSAs by NSSA ABRs and are flooded throughout the
whole routing domain. Summarization and filtering are supported during the
translation.
Use NSSA to simplify administration if you are an Internet Service Provider (ISP) or
a network administrator and must connect a central site that uses OSPF to a remote
site that uses a different routing protocol. With NSSA, you can extend OSPF to cover
the remote connection by defining the area between the corporate router and the
remote router as an NSSA.
1. To specify area parameters needed to configure OSPF NSSA, use the area nssa
command in Router Configuration mode, as shown below:
MOT(config-ospf)#area <area-id> nssa [default-information-originate]
[no-redistribution] [no-summary] <cr>
where:
area-id identifies the NSSA.
default-information-originate allows Type 7 LSAs to be imported into the
NSSA.
no-redistribution indicates no routes are redistributed to this NSSA.
no summary disallows summary LSAs into the NSSA.
2. To control summarization and filtering of Type 7 LSA into Type 5 LSA during
translation, use the optional summary-address in Router Configuration mode, as
shown below. This command specifies an IP address and address mask that cover
redistributed routes so that one summary route is advertised.
Note: A carriage return entered after the area area-id entry defines the area
as an NSSA.