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Configuring a Stub Area

Stub areas are areas into which OSPF does not flood AS external advertisements. You might want to configure stub areas when much of the topological database consists of AS external advertisements and you want to minimize the size of the topological databases on an area’s routers.

You cannot configure an area as being both a stub area and an NSSA.

To configure a stub area, include the stub statement:



(ospf | ospf3) {


area area-id {

stub <default-metric metric> <(no-summaries | summaries)>;
}


}

For a list of hierarchy levels at which you can configure this statement, see the statement summary section for this statement.

To inject a default route with a specified metric value into the area, include the default-metric option and a metric value. The default route matches any destination that is not explicitly reachable from within the area.

To have the stub areas not advertise summary routes into the stub area, include the no-summaries option. Only the default route is advertised, and only if you include the default-metric option. The default route injected into the not-so-stubby area (NSSA) is a Type 3 LSA.

You must include the stub statement when configuring all routers that are in the stub area.

Note: Beginning with JUNOS Release 8.5, a router-identifier interface that is not configured to run OSPF is no longer advertised as a stub network in OSPF link-state advertisements. For more information about how to configure a router identifier, see Configuring the Router Identifier.

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