CCNA 3 Chapter 10 v6 Exam Answers

Refer to the exhibit. What are three resulting DR and BDR elections for the given topology? (Choose three.)

For segment A, R1 becomes DR because of the priority of 128 of the FastEthernet 0/0 interface. R2 becomes BDR because of the Loopback 0 interface IPv4 address.
For segment B, R3 becomes DR because of the FastEthernet 0/0 interface priority of 255. R5 becomes BDR because of the IPv4 address on the Loopback 0 interface.

A network administrator is troubleshooting an OSPFv3 configuration on an IPv6 network. The administrator issues the show ipv6 protocols command. What is the purpose for this command?

There are various show commands to help troubleshoot or verify OSPFv3, including these:
show ipv6 protocols – used to verify configuration information
show ipv6 ospf neighbor – used to verify that the router has formed an adjacency with its neighboring routers
show ipv6 ospf interface – used to display the OSPFv3 parameters configured on an interface
show ipv6 route ospf – used to display only the OSPFv3 learned routes in the routing table

Refer to the exhibit. What two conclusions can be drawn based on the output of the show ipv6 route command? (Choose two.)

The default route ::/0 is learned from another router (signified by OE2) with the link-local address of FE80::200:CFF:FE3B:7501. The symbol OI indicates that a route is learned from an ABR. Routes 2001:DB8:CAFE:1::/64 and 2001:DB8:CAFE:3::/64 are learned from different link-local addresses and therefore are not from the same router.

A network administrator has just changed the router ID on a router that is working in an OSPFv2 environment. What should the administrator do to reset the adjacencies and use the new router ID?

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.
A network administrator is configuring multiarea OSPFv3 on the routers. The routing design requires that the router RT1 is a DROTHER for the network in Area 0 and the DR for the network in Area 1. Check the settings and status of the routers. What can the administrator do to ensure that RT1 will meet the design requirement after all routers restart?

In a multiarea OSPF network, if the interface priority is the same for all routers, then the router with highest router ID becomes the DR and the router with second highest router ID becomes BDR. Changing the router ID can influence the DR/BDR election. However, for an ABR, the same router ID will be used for DR/BDR elections for multiple areas. In this case, it is better to use the interface priority value to manage the DR/BDR election for different areas, because this value is interface specific.

An administrator is troubleshooting OSPFv3 adjacency issues. Which command would the administrator use to confirm that OSPFv3 hello and dead intervals are matching between routers?​

Refer to the exhibit. Directly connected networks configured on router R1 are not being shared with neighboring routers through OSPFv3. What is the cause of the issue?

Unlike OSPFv2, OSPFV3 does not use the network command to advertise directly attached networks. OSPFv3 is enabled directly on the interface. These networks will be included in advertisements once the command ipv6 ospf process_id area area_id is entered on the interface. The OSPF process_id must match with the ipv6 router ospf command.

Refer to the exhibit. What the amount of time that has elapsed since the router received a hello packet?

The show ip ospf interface command is used to display the OSPF parameters configured on an interface like the process ID; router ID; area, and so forth. In the exhibit the router has a default hello interval of 10 seconds. It also displays that the next hello is due in 6 seconds. Hence, the time elapsed is 4 seconds.

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question. Which routers are the DR and BDR in this topology?

Once OSPF neighbor adjacencies have formed, use the show ip ospf neighbors command to determine which router was elected the DR and which router was elected the BDR. In this scenario, R3 was elected the DR because it had the highest priority (10). R5 was elected the BDR because it had the highest router ID among eligible routers (5.5.5.5). R6 was not eligible to become the BDR because its priority was set to 0.

A network engineer has manually configured the hello interval to 15 seconds on an interface of a router that is running OSPFv2. By default, how will the dead interval on the interface be affected?

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Which command can be used to view the OSPF hello and dead time intervals?

The OSPF hello and dead timers can be configured per interface. Hence, the correct command used to view the timers is the show ip ospf interface command. Adding the interface name and number to the command displays output for a specific interface.

Refer to the exhibit. Which conclusion can be drawn from this OSPF multiaccess network?​

On OSPF multiaccess networks, a DR is elected to be the collection and distribution point for LSAs sent and received. A BDR is also elected in case the DR fails. All other non-DR or BDR routers become DROTHER. Instead of flooding LSAs to all routers in the network, DROTHERs only send their LSAs to the DR and BDR using the multicast address 224.0.0.6. If there is no DR/BDR election, the number of required adjacencies is n(n-1)/2 => 4(4-1)/2 = 6. With the election, this number is reduced to 3.​

Which two parameters must match between neighboring OSPF routers in order to form an adjacency? (Choose two.)

To form a neighbor relationship between OSPF speaking routers, the routers should reside on the same network and have the same hello and dead intervals. Others criteria that must match are area ID and network type.

What three states are transient OPSF neighbor states that indicate a stable adjacency is not yet formed between two routers? (Choose three.)

Only the full and 2way states indicate that a stable adjacency is formed.​ The loading, exstart, and exchange states are transitory states between the 2way and full states.

Refer to the exhibit. What three conclusions can be drawn from the displayed output? (Choose three.)

Which OSPF feature allows a remote OSPF area to participate in OSPF routing when it cannot connect directly to OSPF Area 0?

Refer to the exhibit. A network administrator has configured OSPFv2 on the two Cisco routers but PC1 is unable to connect to PC2. What is the most likely problem?

If a LAN network is not advertised using OSPFv2, a remote network will not be reachable. The output displays a successful neighbor adjacency between router R1 and R2 on the interface S0/0 of both routers.

Refer to the exhibit. R1 and R2 are connected to the same LAN segment and are configured to run OSPFv3. They are not forming a neighbor adjacency. What is the cause of the problem?

There is a mismatch between the timer intervals of R1 and R2. In OSPF the timers must match on two routers before they will become neighbors. The IPv6 addresses that are used by OSPFv3 are link-local, and are in the same subnet. The OSPFv3 process ID is locally significant, and does not have to match between routers. The default OSPF interface priority value is 1, and does not prevent neighbor relationships from forming.

Refer to the exhibit. A network administrator is configuring OSPF for R1 and R2, but the adjacency cannot be established. What is the cause of the issue?

To form a neighbor relationship between OSPF speaking routers, the routers should reside on the same network and have the same Hello and dead intervals. Others criteria that must match are area ID and network type. In the topology displayed, the two routers are in two different areas, thus causing an area mismatch error.

Which command will a network engineer issue to verify the configured hello and dead timer intervals on a point-to-point WAN link between two routers that are running OSPFv2?

The show ip ospf interface serial 0/0/0 command will display the configured hello and dead timer intervals on a point-to-point serial WAN link between two OSPFv2 routers. The show ipv6 ospf interface serial 0/0/0 command will display the configured hello and dead timer intervals on a point-to-point serial link between two OSPFv3 routers. The show ip ospf interface fastethernet 0/1 command will display the configured hello and dead timer intervals on a multiaccess link between two (or more) OSPFv2 routers. The show ip ospf neighbor command will display the dead interval elapsed time since the last hello message was received, but does not show the configured value of the timer.

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When checking a routing table, a network technician notices the following entry:
O*E2 0.0.0.0/0 [110/1] via 192.168.16.3, 00:20:22, Serial0/0/0
What information can be gathered from this output?

The metric towards this external route is one and 192.168.16.3 is the address of the next interface towards the destination.

A network engineer suspects that OSPFv3 routers are not forming neighbor adjacencies because there are interface timer mismatches. Which two commands can be issued on the interface of each OSFPv3 router to resolve all timer mismatches? (Choose two.)

The no ipv6 ospf hello-interval and no ipv6 ospf dead-interval commands issued on each OSPFv3 interface will reset the intervals to the respective default periods. This ensures that the timers on all routers now match and, providing other appropriate configurations are correct, the routers will form adjacencies. The ip ospf hello-interval 10 and ip ospf dead-interval 40 commands are OPSFv2 commands that are used for IPv4 routing. If the ipv6 ospf hello-interval and ipv6 ospf dead-interval commands are used, then the interval has to be specified in seconds. The parameter default is not valid in these commands.

Match each OSPF election criterion to its sequential order for the OSPF DR and BDR election process. (Not all options are used.)

During the DR and BDR election process, the DR will be the one with the highest interface priority. If the priority is not manually configured, there will be a tie on the default value of 1, so the router with the highest router ID will be selected. The router ID is chosen depending on what is configured on the router. A manually configured router ID is preferred, with the highest IPv4 address on a loopback interface being preferred next, followed by the highest IPv4 address on a physical interface.