Not-So-Stubby Area Configuration

Not-So-Stubby Area Configuration
Recall that a not-so-stubby area (NSSA) is useful when there is an area that requires the injection
of external routes from an ASBR, but we still want to eliminate the injection of Type 5 LSAs from
the ABR. Figure 6.7 presents such a scenario. We want to prevent Area 0 from injecting Type 5
LSAs into Area 1, which can be assumed to originate to the right of Area 0 from an unseen ASBR,
yet we still need external routes from the RIP routing process to be injected into Area 1 and propagated
to other OSPF areas. The solution to these requirements is to make Area 1 an NSSA.