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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter27 Configuring OSPF
Customizing OSPF
•Password to provide a clears text password for area authentication, which is not recommended
where security is a concern.
•MD5 to allow MD5 authentication.
Step7 Enter a value in the Default Cost field to specify a default cost for the OSPF area.
Valid values range from 0 to 65535. The default value is 1.
Step8 Click OK.
Configuring OSPF NSSA
The OSPF implementation of an NSSA is similar to an OSPF stub area. NSSA does not flood Type 5
external LSAs from the core into the area, but it can import autonomous system external routes in a
limited way within the area.
NSSA imports Type 7 autonomous system external routes within an NSSA area by redistribution. These
Type 7 LSAs are translated into Type 5 LSAs by NSSA ABRs, which are flooded throughout the whole
routing domain. Summarization and filtering are supported during the translation.
You can simplify administration if you are an ISP or a network administrator that must connect a central
site using OSPF to a remote site that is using a different routing protocol using NSSA.
Before the implementation of NSSA, the connection between the corporate site border router and the
remote router could not be run as an OSPF stub area because routes for the remote site could not be
redistributed into the stub area, and two routing protocols needed to be maintained. A simple protocol
such as RIP was usually run and handled the redistribution. 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.
Before you use this feature, consider these guidelines:
•You can set a Type 7 default route that can be used to reach external destinations. When configured,
the router generates a Type 7 default into the NSSA or the NSSA area boundary router.
•Every router within the same area must agree that the area is NSSA; otherwise, the routers will not
be able to communicate.
To specify area parameters for your network to configure OSPF NSSA, perform the following steps:
Step1 From the main ASDM home page, choose Configuration > Device Setup > Routing > OSPF > Setup.
Step2 Click the Area/Networks tab.
Step3 Click Add.
The Add OSPF Area dialog box appears.
Step4 Click the NSSA radio button in the Area Type area.
Choose this option to make the area a not-so-stubby area. NSSAs accept Type 7 LSAs. When you create
the NSSA, you have the option of preventing summary LSAs from being flooded into the area by
unchecking the Summary check box. You can also disable route redistribution by unchecking the
Redistribute check box and checking the Default Information Originate check box.
Step5 Enter the IP address in the IP Address field of the network or host to be added to the area. Use 0.0.0.0
with a netmask of 0.0.0.0 to create the default area. You can only enter 0.0.0.0 in one area.