Connecting Networks Version 6 – CN Pretest Exam

Connecting Networks (Version 6.00) – CN Pretest Exam

QUESTION 1

The graphic displays the following:
Router R1 is connected to PC1 and has the IP address 192.168.10.254 on interface Fa0/0. PC1 has the IP address 192.168.10.1 /24.
Router R1 S0/0 has IP address 192.168.20.1 /30 and is connected to router R2 on interface S0/0 with IP address 192.168.20.2 /30.
Router R2 is connected to PC1 and has the IP address 192.168.30.254 on interface Fa0/0. PC2 has the IP address 192.168.30.1 /30.
Below the topology is a router prompt and command, and some partial command output:
R2# show ip protocols

Routing Protocol is “ospf 99”
Router ID 192.168.30.254
Maximum path: 4
Routing for Networks:
192.168.20.2 0.0.0.0 area 0
192.168.3.0 0.0.0.255 area 0
Passive Interface(s):
FastEthernet0/0
Routing Information Sources:
Gateway Distance Last Update
192.168.20.1 110 00:02:11
192.168.30.254 110 00:02:11
Distance: (default is 110)
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?


Interface Fa0/0 is configured as a passive-interface on router R2.
Interface S0/0 is configured as a passive-interface on router R2.
Interface Fa0/0 has not been activated for OSPFv2 on router R2.*
Interface s0/0 has not been activated for OSPFv2 on router R2.

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.

QUESTION 2

What three states are transient OPSF neighbor states that indicate a stable adjacency is not yet formed between two routers? (Choose three.)
established
loading*
2way
exstart*
full
exchange*

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.

 

QUESTION 3

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?
show ipv6 ospf interface​*
show ipv6 ospf​
show ipv6 ospf neighbor​
show ipv6 protocols​

 

QUESTION 4

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 route is located two hops away.
The metric for this route is 110.
The edge of the OSPF area 0 is the interface that is addressed 192.168.16.3.
This route is a propagated default route.*

 

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

 

QUESTION 5

Two CLI outputs display, respectively, as follows:
R1# show ipv6 ospf interface fa0/0
FastEthernet0/0 is up, line protocol is up
Link Local Address FE80::21E:BEFF:FEF4:55C8, Interface ID 4
Area 0, Process ID 10, Instance ID 0, Router ID 1.1.1.1
Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 1.1.1.1, local address FE80::21E:BEFF:FEF4:55C8
No backup designated router on this network
Timer intervals configured, Hello 1, Dead 4, Wait 4, Retransmit 5
R2# show ipv6 ospf interface fa0/0
FastEthernet0/0 is up, line protocol is up
Link Local Address FE80::21E:7AFF:FE5F:6650, Interface ID 4
Area 0, Process ID 1, Instance ID 0, Router ID 2.2.2.2
Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 2.2.2.2, local address FE80::21E:7AFF:FE5F:6650
No backup designated router on this network
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

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?

 


The IPv6 addresses of R1 and R2 are not in the same subnet.
The priority value of both R1 and R2 is 1.
The timer intervals of R1 and R2 do not match.*
The OSPFv3 process IDs of R1 and R2 are different.

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.

QUESTION 6

The graphic shows some partial output of the show running-config command:R1# show running-config

ipv6 unicast-routing
!
interface GigabitEthernet0/0
no ip address
ipv6 address 2001:DB8:CAFE:A001::1/64
ipv6 ospf 10 area 0
!
interface GigabitEthernet0/1
no ip address
ipv6 address 2001:DB8:CAFE:1::1/64
ipv6 ospf 10 area 0
!
ipv6 router ospf 1
router-id 1.1.1.1
log-adjacency-changes
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?

 


There are no network statements for the routes in the OSPF configuration.
The no shutdown command is missing on the interfaces.
IPv6 OSPF routing is not enabled.
There is a mismatch of OSPF process ID in commands.*

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.

QUESTION 7

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?

DR:R6 BDR:R5
DR:R1 BDR:R2
DR:R5 BDR:R3
DR:R3 BDR:R6
DR:R3 BDR:R5*
DR:R4 BDR:R1

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.

 

QUESTION 8

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


If the DR stops producing Hello packets, a BDR will be elected, and then it promotes itself to assume the role of DR.​
With an election of the DR, the number of adjacencies is reduced from 6 to 3.*
​When a DR is elected all other non-DR routers become DROTHER.
​All DROTHER routers will send LSAs to the DR and BDR to multicast 224.0.0.5.

 

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.​

QUESTION 9

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?
show ipv6 ospf interface serial 0/0/0
show ip ospf neighbor
show ip ospf interface fastethernet 0/1
show ip ospf interface serial 0/0/0*

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.

 

QUESTION 10

Question as presented:

 

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.

 

QUESTION 11

Which OSPF feature allows a remote OSPF area to participate in OSPF routing when it cannot connect directly to OSPF Area 0?
virtual link*
NBMA
point-to-point connectivity
DR/BDR

 

 

QUESTION 12

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.)
no ipv6 ospf dead-interval*
ip ospf hello-interval 10
no ipv6 router ospf 10
no ipv6 ospf cost 10
no ipv6 ospf hello-interval*
ip ospf dead-interval 40

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.

 

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