lunes, 27 de julio de 2015

CCNA 2 Cisco v5.0 Chapter 8 - Answers

1. Which OSPF component is identical in all routers in an OSPF area after convergence?

adjacency database
link-state database
routing table
SPF tree
Each OSPF router views the network differently as the root of a unique SPF tree. Each router builds adjacencies based on its own position in the topology. Each routing table in the area is developed individually through the application of the SPF algorithm. The link-state database for an area, however, must reflect the same information for all routers.

2. Which three statements describe features of the OSPF topology table? (Choose three.)

It is a link-state database that represents the network topology.
Its contents are the result of running the SPF algorithm.
When converged, all routers in an area have identical topology tables.
The topology table contains feasible successor routes.
The table can be viewed via the show ip ospf database command.
After convergence, the table only contains the lowest cost route entries for all known networks.
The topology table on an OSPF router is a link-state database (LSDB) that lists information about all other routers in the network, and represents the network topology. All routers within an area have identical link-state databases, and the table can be viewed using the show ip ospf database command. The EIGRP topology table contains feasible successor routes. This concept is not used by OSPF. The SPF algorithm uses the LSDB to produce the unique routing table for each router which contains the lowest cost route entries for known networks.

3. What is a function of OSPF hello packets?

to send specifically requested link-state records
to discover neighbors and build adjacencies between them
to ensure database synchronization between routers
to request specific link-state records from neighbor routers
The OSPF hello packet serves three primary functions: discover OSPF neighbors and establish adjacencies, advertise parameters that OSPF neighbors must agree on, and elect the DR and BDR.

4. Which OPSF packet contains the different types of link-state advertisements?

Link-state update (LSU) packets contain different types of link-state advertisements (LSAs). The LSUs are used to reply to link-state requests (LSRs) and to announce new information.

5. A router is participating in an OPSFv2 domain. What will always happen if the dead interval expires before the router receives a hello packet from an adjacent DROTHER OPSF router?

OSPF will run a new DR/BDR election.
SPF will run and determine which neighbor router is “down”.
A new dead interval timer of 4 times the hello interval will start.
OSPF will remove that neighbor from the router link-state database.
On Cisco routers the default dead interval is 4 times the hello interval, and this timer has expired in this case. SPF does not determine the state of neighbor routers; it determines which routes become routing table entries. A DR/DBR election will not always automatically run; this depends on the type of network and on whether or not the router no longer up was a DR or BDR.

6. What are the two purposes of an OSPF router ID? (Choose two.)

to facilitate the establishment of network convergence
to uniquely identify the router within the OSPF domain
to facilitate the transition of the OSPF neighbor state to Full
to facilitate router participation in the election of the designated router
to enable the SPF algorithm to determine the lowest cost path to remote networks
OSPF router ID does not contribute to SPF algorithm calculations, nor does it facilitate the transition of the OSPF neighbor state to Full. Although the router ID is contained within OSPF messages when router adjacencies are being established, it has no bearing on the actual convergence process.

7. Which criterion is preferred by the router to choose a router ID?

the IP address of the highest configured loopback interface on the router
the IP address of the highest active interface on the router
the router-id rid command
the IP address of the highest active OSPF-enabled interface
The preferred order of criteria for Cisco routers to identify the router ID is: an explicitly configured router using the router-id rid command; the IP address of any configured loopback interface; and the IP address of any active interface on the router (it does not have to be an OSPF-enabled interface).

8. Which wildcard mask would be used to advertise the network as part of an OSPF configuration?
The wildcard mask can be found by subtracting the subnet mask from

9. Which command should be used to check the OSPF process ID, the router ID, networks the router is advertising, the neighbors the router is receiving updates from, and the default administrative distance?

show ip protocols
show ip ospf neighbor
show ip ospf
show ip ospf interface
The show ip ospf neighbor command is used to verify that the router has formed an adjacency with its neighboring routers. The show ip ospf command displays the OSPF process ID and router ID, the OSPF area information, as well as the last time the SPF algorithm was calculated. The show ip ospf interface command provides detailed information about every OSPF-enabled interface.

10. Which OSPFv3 function works differently from OSPFv2?

metric calculation
hello mechanism
OSPF packet types
election process
Both versions of OSPF use the same five basic packet types, the cost metric, and the DR/BDR election process. Hello packets are used in both versions to build adjacencies. OSPFv3, however, uses advanced encryption and authentication features that are provided by IPsec, while OSPFv2 uses either plain text or MD5 authentication.

11. Which three statements describe the similarities between OSPFv2 and OSPFv3? (Choose three.)

They both are link-state protocols.
They both use the exit interface address as the source address when sending OSPF messages.
They both share the concept of multiple areas.
They both support IPsec for authentication.
They both use the same DR/BDR election process.
They both have unicast routing enabled by default.
Only OSPFv2 messages are sourced from the IP address of the exit interface; OSPFv3 uses the link-local address of the exit interface. Only OSPFv3 uses IPsec; OSPFv2 uses plain text or MD5 authentication. Unicast routing is enabled by default only with OSPFv2.

12. What does a Cisco router use automatically to create link-local addresses on serial interfaces when OSPFv3 is implemented?

the highest MAC address available on the router, the FE80::/10 prefix, and the EUI-48 process
the FE80::/10 prefix and the EUI-48 process
the MAC address of the serial interface, the FE80::/10 prefix, and the EUI-64 process
an Ethernet interface MAC address available on the router, the FE80::/10 prefix, and the EUI-64 process
Since serial interfaces do not have MAC addresses, OSPFv3 automatically assigns a link-local address to them derived from the first available MAC address from the pool of Ethernet interface addresses on the router. A FE80::/10 prefix is added. The router then applies the EUI-64 process to the MAC address by inserting FFFE into the middle of the existing 48-bit address and flipping the seventh bit.

13. A network administrator enters the command ipv6 router ospf 64 in global configuration mode. What is the result of this command?

The router will be assigned an autonomous system number of 64.
The router will be assigned a router ID of 64.
The reference bandwidth will be set to 64 Mb/s.
The OSPFv3 process will be assigned an ID of 64.
The basic command to implement OSPFv3 on a router uses the same process-id parameter as OSPFv2 to assign a locally-significant number to the OSPF process. OSPF does not use autonomous system numbers. Following the assignment of the process ID, a prompt will direct the user to manually assign a router ID. After the router ID is assigned, the reference bandwidth can be set.

14. When a network engineer is configuring OSPFv3 on a router, which command would the engineer issue immediately before configuring the router ID?

ipv6 ospf 10 area 0
ipv6 router ospf 10
interface serial 0/0/1
clear ipv6 ospf process
The OSPFv3 router ID is configured in the IPv6 router configuration mode. The clear ipv6 ospf process privileged EXEC command forces OSPF on the router to renegotiate neighbor adjacencies. The interface serial 0/0/1 command causes the router to enter interface configuration mode where OSPFv3 is enabled by issuing the ipv6 ospf process-id area area-id command.

15. Single area OSPFv3 has been enabled on a router via the ipv6 router ospf 20 command. Which command will enable this OSPFv3 process on an interface of that router?

ipv6 ospf 0 area 0
ipv6 ospf 20 area 20
ipv6 ospf 0 area 20
ipv6 ospf 20 area 0
The command to enable an OSPFv3 process on a router interface is ipv6 ospf process-id area area-id. In the case the process ID is 20 and the area ID is 0.

16. Which command will verify that a router that is running OSPFv3 has formed an adjacency with other routers in its OSPF area?

show running-configuration
show ipv6 ospf neighbor
show ipv6 route ospf
show ipv6 interface brief
The show ipv6 ospf neighbor command will verify neighbor adjacencies for OSPFv3 routers. The other options do not provide neighbor information.

17. Which command will provide information specific to OSPFv3 routes in the routing table?

show ip route ospf
show ip route
show ipv6 route
show ipv6 route ospf
The show ipv6 route ospf command gives specific information that is related to OSPFv3 routes in the routing table. The show ipv6 route command will show the entire routing table. The show ip route and show ip route ospf commands are used with OSPFv2.

18. Fill in the blank.

The election of a DR and a BDR takes place on multiaccess networks, such as Ethernet networks.
There is no need to have a DR/BDR election on a point-to-point link.

19. Fill in the blank.

OSPF uses cost as a metric.
The OSPF metric is cost. The lowest cost path to a remote destination is the preferred path and is installed in the routing table.

20. Fill in the blank. Do not use abbreviations.

To quickly verify OSPFv3 configuration information including the OSPF process ID, the router ID, and the interfaces enabled for OSPFv3, you need to issue the command show ipv6 protocols.


Question as presented:
Match the information to the command that is used to obtain the information. (Not all options are used.)
Place the options in the following order:
Neighbor ID of 
– not scored – 
Routing Process “ospf 10″ with ID 
Routing Protocol is “ospf 10″ 
BW 1544 Kbit/sec


Question as presented:
By order of precedence, match the selection of router ID for an OSPF-enabled router to the possible router ID options. (Not all options are used.)
Place the options in the following order:
Third precedence 
Fourth precedence 
- not scored -
First precedence 
Second precedence
Cisco routers determine the OSPF router ID based on the preferential order of configured router ID, IPv4 addresses of loopback interfaces, and IPv4 addresses of active physical interfaces.


Question as presented:
Match the description to the term. (Not all options are used.)
Place the options in the following order:

This is where the details of the neighboring routers can be found. 
This is the algorithm used by OSPF. 
All the routers are in the backbone area. 
– not scored – 
This is where you can find the topology table. 
– not scored -
DUAL is the algorithm used by EIGRP. In multiarea OSPF, OSPF is implemented using multiple areas, and all of them must be connected to the backbone area.


Open the PT Activity. Perform the tasks in the activity instructions and then complete the task.
What message is displayed on

The correct configuration on R1 is:
router ospf 10
network area 0
network area 0
The correct configuration on R2 is:
router ospf 10
network area 0
network area 0
network area 0

Espero haber ayudado en algo. Hasta la próxima oportunidad!

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