Hello there! I can not leave the OSPF subject because  it is too beautiful to abandon it. In this post I try to demonstrate how the LSAs work in different OSPF scenarios. In the last post I wrote what is the LSAs, which network type is available, and which router types are exist in an OSPF network. But I do not described these things. On this post I try to define these topics better.  To understand that LSAs how can be flooded on different areas you need to understand the area types. As I mentioned before, there is 5 type of area exist of OSPF. Basically in a backbone/regular area the following LSA types will be flooded: Type 1 Router LSA Type 2 Network LSA Type 3 ABR Summary LSA - if ABR exist in the area. Type 4 ASBR Network LSA - if ASBR exist in the area. Type 5 ASBR Summary LSA - if ASBR exist in the area.  Backbone area is special, because it is responsible for the other area can be connected each other. And what about stub area? Stub types of areas help us to redu...