OSPF-2

Question 1

What are the different neighbor states in OSPF?

Answer 1

1. Down: No Hello packet has been received from a previous “Full” Neighbor.
2. Attempt: Used for a manually configured neighbor.
3. Init: Hello packet received from a new neighbor.
4. 2-Way: Identifies compatible neighbors (non-DR/BDR relationships may stop here).
5. Exstart/Exchange: Master/Slave relationship determined and DBDS exchanged.
6. Loading: The LSR/LSA/LSU exchanges.
7. Full: Full State.

Question 2

Explain different OSPF LSA Types?

Answer 2

1. Router LSA (Type1) - Each router generates a Type 1 LSA that lists its active interfaces, IP addresses, neighbors, and the cost. LSA Type 1 is flooded only within an area.
2. Network LSA (Type2 - Type2 LSA is sent out by the designated router (DR) and lists all the routers on the segment it is adjacent to. Type 2 LSA is flooded only within an area.
3. Summary LSA (Type3) - Type 3 LSAs are generated by Area Border Routers (ABRs) to advertise networks from one area to the rest of the areas in the Autonomous System.
4. Summary ASBR LSA (Type4) - Generated by the ABR. It contains routes to ASBRs.
5. External LSA (Type5) - External LSAs are generated by ASBRs and contain routes to networks that are external to the current Autonomous System.
6. Not-So-Stubby Area LSA (Type 7) - Stub areas do not allow Type 5 LSAs. A Not So Stubby Area (NSSA) allows the advertisement of Type 5 LSA as Type 7 LSAs. An ASBR generates type LSA inside a Not So Stubby Area (NSSA) to describe routes redistributed into the NSSA.

Question 3

Explain different OSPF Network types.

Answer 3

1. Broadcast
2. Non-Broadcast (NBMA)
3. Point-to-Point
4. Point-to-multipoint
5. Point-to-multipoint non-broadcast

Question 4

What are the benefits of doing route summarization?

Answer 4

1. Smaller routing table.
2. Summarizes pool of addresses into one prefix.
3. Lessens the load on router processor and memory resources.
4. Less number of update messages.
5. Less bandwidth.

Question 5

What is Route Redistribution?

Answer 5

Route redistribution is the process of taking routes learned via one routing protocol and injecting those routes into another routing protocol domain.