Ccna certification Practice Tests

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Appendix 

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  Answers to Practice Test Questions

 169.  D.  OSPF updates are event triggered. These events could be a neighbor router not 

responding or a route going down. OSPF is a link-state protocol and not a distance-vector 

protocol. OSPF does not perform auto-summarization of routes. OSPF multicasts changes 

to links, and each router calculates changes to its own routing table.

 170.  B.  The highest IP address configured on all of the loopback interfaces is chosen first. If a 

loopback is not configured, then the highest IP address on an active interface is chosen. 

However, if a RID is statically set via the OSPF process, it will override all of the above. 

The RID is always the highest IP address configured, not the lowest. The MAC address is 

not relevant to OSPF for the calculation of the RID.

 171.  C.  A link is a routed interface that is assigned to a network and participates in the OSPF 

process. This link will be tracked by the OSPF process for up/down information as well as 

the network it is associated with. Just because two routers are participating in OSPF does 

not mean they form a link. Routers sharing the same area ID does not dictate that they 

will form a link. Autonomous system (AS) numbers are not used with OSPF; therefore, 

this is an incorrect answer.

 172.  B.  Adjacencies are formed between the designated router (DR) and its neighbors on 

the same area. This is done to ensure that all neighbor routers have the same Link 

State Database (LSDB). Adjacencies are not formed between routers on the same link, 

same autonomous system (AS), and same OSPF area unless one is the DR and they are 

connected on the same LAN.

 173.  D.  The designated router is elected by the highest priority in the same area. If the 

priorities are all the same, then the highest RID becomes the tiebreaker. OSPF will elect 

a DR for each broadcast network, such as a LAN. This is to minimize the number of 

adjacencies formed. A DR is never elected by the lowest priority or lowest RID.

 174.  B.  The neighborship database is where all of the routers can be found that have responded 

to hello packets. The neighborship database contains all of the routers by RID, and each 

router participating in OSPF manages its own neighborship database. The route table 

database is what the router’s route decisions are based upon. The topological database is 

the link-state database in OSPF. The link-state database contains all the active links that 

have been learned.

 175.  C.  OSPF uses areas to create a hierarchal structure for routing. This structure begins  

with the backbone area of 0. All other areas connect to it to form a complete autonomous 

system (AS). This enables scalability with OSPF, since each area works independently. 

OSPF operates within an autonomous system such as an organization. OSPF uses process 

IDs so that OSPF can be reset by clearing the process. OSPF uses router IDs (RIDs) so that 

a designated router can be elected.

 176.  D.  A LAN is an example of a broadcast multi-access network. All nodes in a network 

segment can hear a broadcast and have common access to the local area network (LAN). 

In OSPF, a broadcast (multi-access) network requires a DR and BDR. An X.25 network 

is a legacy network connectivity method that can provide packet switching. Frame Relay 

by default is a nonbroadcast multi-access (NBMA) connectivity method. Asynchronous 

Transfer Mode (ATM) is a legacy network connectivity method that acts as an NBMA 

network.

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Chapter 3: IP Connectivity (Domain 3)