area ospf3–area-id stub/area ospf3–area id nssa

Syntax

area ospf3-area-id stub [ metric-cost 0 - 16777215 ][ no-summary ]

area ospf3-area-id nssa [metric-cost 0 - 16777215 ][no-summary]

Options

ospf3-area-id

Same area ID as in area [ospf3–area-id|backbone][ normal ], except you cannot assign a backbone area number (0 or 0.0.0.0) to a stub or NSSA area.

stub/nssa

Designates the area identified by ospf3-area-id as a stub area or NSSA.

metric-cost 0 - 16777215

If the routing switch is used as an ABR for the designated area, assigns the cost of the default route (to the backbone) that is injected into the area.

NOTE:

If the routing switch is not an ABR for a stub area or NSSA, the above cost setting is still allowed, but is not used.

In the default configuration, a routing switch acting as an ABR for a stub area or NSSA injects type-7-LSA default routes into the area. If no-summary is configured on the ABR, it injects inter-area-prefix-LSA routes into the area.

metric-type [type1|type2]

Used in NSSA ABRs only. Specifies the type of external cost metric to include in type-7-LSAs advertised for redistribution of external routes in the NSSA.

The metric-type command specifies whether to include the redistribution cost in the cost metric calculation for a type-7-LSA default route injected into the area.

type1 : Calculate external route cost for a type-7-LSA default route as the sum of (1) the external route cost assigned by the ASBR plus (2) the internal cost from the router with traffic for the external route to the ASBR advertising the route.

type2 : Use the external route cost assigned by the ASBR advertising the route.

Default: Enabled with metric-type type2.

NOTE:

Different routers in the NSSA can be configured with different metric-type values.

no-summary

Where the routing switch is an ABR for a stub area or an NSSA, this option reduces the amount of LSA traffic entering the area from the backbone by replacing the injection of inter-area-prefix-LSA routes and type-7-LSA default external routes with injection of an inter-area-prefix-LSA default route.

Default: Disabled

Using no area ospf3-area-id nssa no-summary resets the routing switch to the state where injection of inter-area-prefix-LSA routes and the type-7-LSA default external routes is enabled with metric-type set to type2.

Example input

Creating stub area and NSSA assignments

The following examples of configuring a stub area and an NSSA on a routing switch use an (arbitrary) cost of "15."

Switch(ospf3)# area 2 stub metric-cost 15

Assigns a stub area with a cost of 15.

Switch(ospf3)# area 3 nssa metric-cost 15

Assigns an NSSA with a cost of 15 and, by default, uses a Network-LSA default cost metric for Type-7-LSA (external) routes received from the backbone.

Switch(ospf3)# area 4 nssa metric-cost 15 no-summary

Assigns an NSSA with a cost of 15, blocks injection of Inter-Area-Prefix- LSA routes, and starts injection of Inter-Area-Prefix-LSA default routes from the backbone.

Switch(ospf3)# area 5 nssa metric-cost 15 metric-type type1

Sets the cost metric type for Type-7- LSA default routes injected into the NSSA.