Packets: Hello, Database description packets, LSA, LSA Update. Explain in detail . If asked in 1 line , reply accordingly. LSA Study: Learn the types. Draw a toplogy running ospf. Mark areas and router types. Start with one area, list all possible LSA for a given routers within that area. Once done , do the same for all routers in that area and then move on to other areas in the same AS. This gives fair understanding of OSPF protocol. States: Down, init , 2 way, exstart, exchange, loading, established. Better to know in which scenario the neighbors may get stuck in each state. Exstart state(MTU mismatch).