
Configuring OSPF Areas and Global Settings
Table 21 lists the parameters for areas and global settings that you use when configuring OSPF on your system. As you add areas, each is displayed with its own configuration parameters under the Areas section.
Table 21 OSPF Area Configuration Parameters
Parameter | Description |
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|
Add New | You can configure any area with any number of address ranges. Use these ranges to |
Address Range | reduce the number of routing entries that a given area emits into the backbone and |
| thus all areas. If a given prefix aggregates a number of more specific prefixes within |
| an area, you can configure an address that becomes the only prefix advertised into |
| the backbone. You must be careful when configuring an address range that covers |
| parts of a prefix not contained within the area. By definition, an address range consists |
| of a prefix and a mask length. |
| Note: You can prevent a specific prefix from being advertised into the backbone, by |
| selecting On in the Restrict field next to the entry for that prefix. |
Add New Stub | OSPF can advertise reachability to prefixes that are not running OSPF using a stub |
Network | network. The advertised prefix appears as an OSPF internal route and can be filtered |
| at area borders with the OSPF area ranges. The prefix must be directly reachable on |
| the router where the stub network is configured; that is, one of the router's interface |
| addresses must fall within the prefix to be included in the |
| stub hosts by specifying a mask length of 32. |
| This feature also supports advertising a prefix and mask that can be activated by the |
| local address of a |
| address, enter an IP address for the prefix and a cost with a value other than zero. |
Area Type | Choose Normal, Stub, or NSSA. For descriptions of area types, see “Types of Areas” |
| on page 354. |
|
|
Table 22 describes the configuration parameters for stub areas. These fields appear if you define the area as a stub area.
Table 22 Stub Area Parameters
Parameter | Description |
|
|
Cost for Default Route | Enter a cost for the default route to the stub area. Range: |
| is no default. |
Import Summary Routes | Specifies if summary routes (summary link advertisements) are imported into |
| the stub area or NSSA. Each summary link advertisement describes a route |
| to a destination outside the area, yet still inside the AS (i.e. an |
| route). These include routes to networks and routes to AS boundary routers. |
| Default: On. |
|
|
Table 23 describes the configuration parameters for NSSA areas. These fields appear if you define the area as an NSSA (Not So Stubby Area). For more information on NSSA, see RFC 3101.
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