Configuring OSPF Areas

Use the following commands to configure OSPF areas, including the backbone and stub areas.

For OSPFv2, use the following commands.

set [instance <Instance Name>] ospf area backbone {off | on}

set ospf area <OSPF Area>

      {off | on}

      stub {off | on}

      stub default-cost <1-677215>

      stub summary {off | on}

      nssa {off | on}

      nssa default-cost <1-677215>

      nssa default-metric-type <1-2>

      nssa import-summary-routes {off | on}

      nssa translator-role {always | candidate}

      nssa translator-stability-interval <1-65535>

      nssa redistribution {off | on}

      nssa range <Range of IP Addresses> [restrict] {off | on}

Parameters:

Parameter

Description

backbone {off | on}

Specifies whether to enable or disable the backbone area.

By default, the backbone area is enabled.

You can disable the backbone area if the system does not have interfaces on the backbone area.

{off | on}

Specifies the area ID for a new OSPF area.

The area ID 0.0.0.0 is reserved for the backbone.

Best Practice - We recommend that you enter the area ID as a dotted quad, but you can use any integer as the area ID.

stub {off | on}

Specifies the area ID for a stub area. Stub areas are areas that do not have AS external routes.

Note - The backbone area cannot be a stub area.

stub default-cost <1-677215>

Specifies a default route into the stub area with the specified cost.

stub summary {off | on}

Specifies the OSPF area as totally stubby, meaning that it does not have any AS external routes and its area border routers do not advertise summary routes.

nssa {off | on}

Specifies the area ID for an NSSA.

Note - The backbone area cannot be an NSSA area.

nssa default-cost <1-677215>

Specifies the cost associated with the default route to the NSSA.

nssa default-metric-type <1-2>

Specifies the type of metric.

  • 1 - Route is internal and its metric can be used directly by OSPF for comparison.

  • 2 - Route is external and its metric cannot be used for comparison directly.

nssa import-summary-routes {off | on}

Specifies if summary routes (summary link advertisements) are imported into the NSSA.

nssa translator-role {always | candidate}

Specifies whether this NSSA border router will unconditionally translate Type-7 LSAs into Type-5 LSAs.

  • always - Type-7 LSAs are translated into Type-5 LSAs regardless of the translator state of other NSSA border routers.

  • candidate- This router participates in the translator election to determine if it will perform the translations duties.

nssa translator-stability-interval <1-65535>

Specifies how long in seconds this elected Type-7 translator will continue to perform its translator duties once it has determined that its translator status has been assumed by another NSSA border router.

Default: 40 seconds.

nssa redistribution {off | on}

Specifies if both Type-5 and Type-7 LSAs or only Type-7 LSAs will be originated by this NSSA border router.

nssa range <Range of IP Addresses> [restrict] {off | on}

Specify the range of addresses to reduce the number of Type-5 LSAs for the NSSA border router.

To prevent a specific prefix from being advertised, use the restrict argument.