We explore in this session the operation of NSSA and totally NSSA areas (NSSA no-summary) what LSA types they filter, how Type 7 LSA are translated to Type 5 LSA and how routing is done within these areas

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Video Description

NSSA - Not-So-Stubby Area
Filters Type 4 and 5 LSA
ABRs do not originate a default route.
External routes are allowed inside the area (type 7 LSA)
The ABR with the highest router-id translates the type 7 LSA to type 5 when they are sent to the backbone area (0).

Logic inside this area:
Routers know how to reach the ABR, the ABR knows how to reach the ASBRs and the ASBR know how to reach external routes. If all of the traffic is sent to the ABR, the more specific information is not needed.

Totally Stub (no-summary)
Behaves just like the NSSA but additionally filters type 3 LSAs.
The ABR originate a default route with a type 3 LSA

Logic inside this area:
The same as with NSSA areas with the difference that now it applies to all of the traffic going outside of the area. The ABR know how to reach any point of the network, all traffic will be sent to them and the more specific information is not needed.



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