OSPF - NSSA no automatic default route

When deploying OSPF using an NSSA stub area, the ABR will not automatically create a default route as it would in other stub area types.

An NSSA allows us to have an ASBR in our stub area. If you have an ASBR, there are now two possible exit points from the area, via the ABR to the rest of the OSPF domain, or out of the ASBR to a routing domain external to OSPF. So the configuration of the default route is left up to the network engineer to implement manually.

The configuration of the default route must be done manually using the default-information-originate feature of OSPF.

https://networklessons.com/ospf/how-to-configure-ospf-nssa-not-so-stubby-area