Cisco ASA 5505 Configuration Manual page 397

Chapter 21 Configuring OSPF
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
Step 4
with a netmask of 0.0.0.0 to create the default area. You can only enter 0.0.0.0 in one area.
Step 5 Enter the network mask in the Network Mask field for the IP address or host to be added to the area. If
adding a host, choose the 255.255.255.255 mask.
Step 6 Choose the OSPF Authentication type.
Choices include:
•
•
•
Step 7 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.
Click OK.
Step 8
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:
•
•
To specify area parameters for your network as needed to configure OSPF NSSA, perform the following
steps:
Step 1 From the main ASDM home page, choose Configuration > Device Setup > Routing > OSPF > Setup.
Step 2 Click the Area/Networks tab.
Click Add.
Step 3
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None—This option disables OSPF area authentication. This is the default setting.
Password—This option provides a clears text password for area authentication. This option is not
recommended where security is a concern.
MD5—This option allows MD5 authentication.
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.
Cisco ASA 5500 Series Configuration Guide using ASDM
Customizing OSPF
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