ENSGRPWhen dealing with stub areas in OSPF, the ABR will suppress type 4 and 5 LSA’s. To maintain connectivity the ABR will advertise a default route as a summary LSA (TYPE-3).
For NSSA, a default route is not propagated by default. You must explicitly tell the ABR to send the default route into the NSSA area. This default route will be a NSSA external route ( Type-7).
router ospf <process_id>
area <area_id> nssa default-information-originate
The above output will generate NSSA Type-2 external default route (LSA type-7).
The metric type for the default route above can be changed to a Type 1 with the metric-type command.
router ospf <process_id>
area nssa <area_id> default-information-originate metric-type 1
If the area is set to NSSA totally stuby area. An Inter-area default route will be created on the ABR and sent to the NSSA totally stubby area.
router ospf 1 area
nssa <area_id> default-information-originate no-summary
The cost of the default route can be manually set as follows.
router ospf <process_id>
area <area_id> default-cost <cost>
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