Stub Area/ Totally Stub/ Stub Receive Only/ NSSA

Altought I have spent many hours trying to understand Stub areas, I still don't understand it. Could you explain me :

- Stub Area

- Totally Stub Area

- Stub Receive Only

- NSSA

Thanks in advance, Regards, Hervé

Stub Area - An OSPF ABR does not pass external routes into the Stub Area. Instead, a default route is passed into the stub area.

Totally Stub Area - An OSPF ABR does not pass either external, nor inter-area routes into a Totally Stubby area. Instead, a default route is passed into the totally stubby area.

NSSA - A router that is part of either a stub area or a totally stubby area cannot also function as an ASBR and import external routes into the OSPF (stub-total stub) area. NSSA allows a router to not only participate in an area that is 'stub' aware, but also function as an ASBR and redistribute external routes into that (stub-like) area.

Stub Receive Only - I beleive this is an EIGRP function. The command instructs a neighbor router to not issue a querry to this router when attempting to converge when a route is lost. Receive only is an additional argument that instructs this router to not advertise any routes it is aware of the its neighbors, but listen to advertisements from its neighbors.

-ja