CCNP Route FAQ: Using OSPF in a Single Area
Q1. What information is held in the topology table?
Q2. What command is used to manually determine which router on a LAN will become the DR?
Q3. What details are used to determine the metric of a route in OSPF by default on a Cisco router?
Q4. It is possible to have more than one OSPF process on a router—how would this be achieved?
Q5. Which RFC identifies the use of OSPF over an NBMA cloud?
Q6. State the different types of packets used to build a routing table for the first time.
Answer: Five packets are used to build the routing table for the first time:
- The Hello protocol—This is used to find neighbors and to determine the designated and backup designated router. The continued propagation of the Hello protocol maintains the transmitting router in the topology database of those that hear the message.
- The database descriptor—This is used to send summary information to neighbors to synchronize topology databases.
- The link-state request—This is a request for more detailed information, which is sent when the router receives a database descriptor that contains new information.
- The link-state update—This is the link-state advertisement (LSA) packet issued in response to the request for database information in the link-state request packet.
- The link-state acknowledgement—This acknowledges the link-state update.
Q7. In creating an adjacency, what is the exstart state?
Q8. Explain the command ip ospf network non-broadcast.
Q9. In which of the NBMA configuration choices is it necessary to manually state the neighbors? Why is this necessary?
It is necessary to define the neighbors to the network because the network believes that it is a nonbroadcast medium, so it cannot send out the multicast traffic to ascertain the neighbors.
Q10. In a Frame Relay environment, which is fully meshed, which OSPF configurations might be chosen? Give reasons for your choice.
Q11. How often by default does OSPF send out hello packets on a broadcast multiaccess link?
Q12. What is a neighbor in OSPF?
Q13. What is an adjacency in OSPF?
Q14. If the network is stable and sees no changes, how often will it send LSAs? Why are these updates sent out periodically?
Q15. If a router has an OSPF priority set to 0, what does this indicate?
Q16. What does NBMA stand for?
Q17. RFC 2328 describes the operation of OSPF in two modes across an NBMA cloud. What are they?
Q18. The Cisco solution point-to-point mode does not require the configuration of DR and BDR. Explain briefly why.
Q19. The address 18.104.22.168 has been allocated to an interface on the router. This interface alone is to be included in the OSPF process. State the command that would start the process on this interface.
Q20. What command would identify the designated router for your LAN?
Q21. The metric used by OSPF is cost. How would you change the default setting on an interface?
Q22. If the command ip ospf network non-broadcast is used, what additional statement is necessary?
Q23. What command shows which router on a LAN is the BDR?
Q24. Explain briefly what show ip ospf database will reveal.
Q25. What command is used to show the state of adjacencies?
Q26. It is possible to have more than one OSPF process on a router. Which command would achieve this?