OSPF NSSA ABR advertises default route

In an NSSA OSPF topology, the following command will generate a Type 7 default route:

router ospf 1
 area 1 nssa default-information-originate

The following rules apply:

• When applied to an NSSA ASBR, this will only generate a default route if:
  • there is a valid default route in the routing table that has been learned through a non-OSPF protocol.
  • the keyword always is added at the end of the command.
• When applied to an NSSA ABR, this will generate a default route with or without a valid default route in the routing table.

Links

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