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DES-7200 Configuration Guide Chapter 4 OSPF
Configuration
4-12
they first use the specified default route.
You should pay attention to the following aspects when you configure a stub area:
The backbone area cannot be configured as a stub area, and the stub area
cannot be used as the transmission area of virtual links.
To set an area as the STUB area, all the routers in the area must be
configured with this feature.
There is no ASBR in stub areas. In other words, the routes outside an
autonomous system cannot be propagated in the area.
To configure the OSPF area parameters, execute the following commands in the
routing process configuration mode:
Command Function
DES-7200 (config-router)#area area-id
authentication
Set plain-text authentication for the area.
DES-7200 (config-router)#area area-id
authentication message-digest
Set MD5 authentication for the area.
DES-7200 (config-router)#area area-id
stub [no-summary]
Set the area as a stub area.
no-summary: Set the area as a stub
area to prevent the ABR between areas
from sending summary-LSAs to the stub
area.
DES-7200 (config-router)#area area-id
default-cost cost
Configure the cost of the default route
sent to the stub area.
Note
For authentication configuration, you need to configure the authentication
parameters on an interface. See “Configuring the OSPF Interface Parameters”
section in this chapter. You must configure the stub area on all the routers in the
area. To configure a full stub area, you also have to configure the full stub area
parameters on the border router of the stub area in addition to the basic
configuration of stub area. You do not need to change the configuration of other
routers.
4.2.5 Configuring the OSPF NSSA
The NSSA (Not-So-Stubby Area) is an expansion of the OSPF stub area. The
NSSA also reduces the consumption of the resources of the routers by preventing
from flooding the type-5 LSA (AS-external-LSA) to the NSSA. However, unlike the
stub area, the NSSA can inject some routes outside the autonomous system to