CISCO CCNA Exam – Q188

What information does a router running a link-state protocol use to build and maintain its topological database? (Choose two.)

A. hello packets
B. SAP messages sent by other routers
C. LSAs from other routers
D. beacons received on point-to-point links
E. routing tables received from other link-state routers
F. TTL packets from designated routers

Correct Answers: A, C

Explanation:
Neighbor discovery is the first step in getting a link state environment up and running. In keeping with the friendly neighbor terminology, a Hello protocol is used for this step. The protocol will define a Hello packet format and a procedure for exchanging the packets and processing the information the packets contain.
After the adjacencies are established, the routers may begin sending out LSAs. As the term flooding implies, the advertisements are sent to every neighbor. In turn, each received LSA is copied and forwarded to every neighbor except the one that sent the LSA.

CISCO CCNA Exam – Q187

Which statements describe the routing protocol OSPF? (Choose three.)

A. It supports VLSM.
B. It is used to route between autonomous systems.
C. It confines network instability to one area of the network.
D. It increases routing overhead on the network.
E. It allows extensive control of routing updates.
F. It is simpler to configure than RIP v2.

Correct Answers: A, C, E

Explanation:
The OSPF protocol is based on link-state technology, which is a departure from the Bellman-Ford vector based algorithms used in traditional Internet routing protocols such as RIP. OSPF has introduced new concepts such as authentication of routing updates, Variable Length Subnet Masks (VLSM), route summarization, and so forth.
OSPF uses flooding to exchange link-state updates between routers. Any change in routing information is flooded to all routers in the network. Areas are introduced to put a boundary on the explosion of link-state updates. Flooding and calculation of the Dijkstra algorithm on a router is limited to changes within an area.

CISCO CCNA Exam – Q186

Refer to the exhibit.
CISCO CCNA Exam – Q186

A network administrator configures a new router and enters the copy startup-config running-config command on the router. The network administrator powers down the router and sets it up at a remote location. When the router starts, it enters the system configuration dialog as shown. What is the cause of the problem?

A. The network administrator failed to save the configuration.
B. The configuration register is set to 0x2100.
C. The boot system flash command is missing from the configuration.
D. The configuration register is set to 0x2102.
E. The router is configured with the boot system startup command.

Correct Answer: A

Explanation:
The “System Configuration Dialog” appears only when no startup configuration file is found. The network administrator has made a mistake because the command “copy startup-config running-config” will copy the startup config (which is empty) over the running config (which is configured by the administrator). So everything configured was deleted.
Note: We can tell the router to ignore the start-up configuration on the next reload by setting the register to 0×2142. This will make the “System Configuration Dialog” appear at the next reload.

CISCO CCNA Exam – Q185

What is the default administrative distance of OSPF?

A. 90
B. 100
C. 110
D. 120

Correct Answer: C

Explanation:
Administrative distance is the feature that routers use in order to select the best path when there are two or more different routes to the same destination from two different routing protocols. Administrative distance defines the reliability of a routing protocol. Each routing protocol is prioritized in order of most to least reliable (believable) with the help of an administrative distance value.

Default Distance Value Table
This table lists the administrative distance default values of the protocols that Cisco supports:
CISCO CCNA Exam – Q185

CISCO CCNA Exam – Q184

Which characteristics are representatives of a link-state routing protocol? (Choose three.)

A. provides common view of entire topology
B. exchanges routing tables with neighbors
C. calculates shortest path
D. utilizes event-triggered updates
E. utilizes frequent periodic updates

Correct Answers: A, C, D

Explanation:
Each of routers running link-state routing protocol learns paths to all the destinations in its “area” so we can say although it is a bit unclear.
Link-state routing protocols generate routing updates only (not the whole routing table) when a change occurs in the network topology so Link-state routing protocol like OSPF uses Dijkstra algorithm to calculate the shortest path.
Unlike Distance vector routing protocol (which utilizes frequent periodic updates), link-state routing protocol utilizes event-triggered updates (only sends update when a change occurs).

CISCO CCNA Exam – Q183

Refer to the exhibit.
CISCO CCNA Exam – Q183

Based on the exhibited routing table, how will packets from a host within the 192.168.10.192/26 LAN be forwarded to 192.168.10.1?

A. The router will forward packets from R3 to R2 to R1.
B. The router will forward packets from R3 to R1 to R2.
C. The router will forward packets from R3 to R2 to R1 AND from R3 to R1.
D. The router will forward packets from R3 to R1.

Correct Answer: C

Explanation:
From the routing table we learn that network 192.168.10.0/30 is learned via 2 equal-cost paths (192.168.10.9 and 192.168.10.5); traffic to this network will be load-balancing.

CISCO CCNA Exam – Q182

Refer to the exhibit.
CISCO CCNA Exam – Q182

C-router is to be used as a “router-on-a-stick” to route between the VLANs. All the interfaces have been properly configured and IP routing is operational. The hosts in the VLANs have been configured with the appropriate default gateway. What is true about this configuration?

A.
These commands need to be added to the configuration:
C-router(config)# router eigrp 123
C-router(config-router)# network 172.19.0.0
B.
These commands need to be added to the configuration:
C-router(config)# router ospf 1
C-router(config-router)# network 172.19.0.0 0.0.3.255 area 0
C.
These commands need to be added to the configuration:
C-router(config)# router rip
C-router(config-router)# network 172.19.0.0
D.
No further routing configuration is required.

Correct Answer: D

Explanation:
Since all the same router (C-router) is the default gateway for all three VLANs, all traffic destined to a different VLA will be sent to the C-router. The C-router will have knowledge of all three networks since they will appear as directly connected in the routing table. Since the C-router already knows how to get to all three networks, no routing protocols need to be configured.

CISCO CCNA Exam – Q181

Refer to the exhibit.
CISCO CCNA Exam – Q181

Why is flash memory erased prior to upgrading the IOS image from the TFTP server?

A. The router cannot verify that the Cisco IOS image currently in flash is valid.
B. Flash memory on Cisco routers can contain only a single IOS image.
C. Erasing current flash content is requested during the copy dialog.
D. In order for the router to use the new image as the default, it must be the only IOS image in flash.

Correct Answer: C

Explanation:
During the copy process, the router asked “Erasing flash before copying? [confirm]” and the administrator confirmed (by pressing Enter) so the flash was deleted.

CISCO CCNA Exam – Q180

Which command would you configure globally on a Cisco router that would allow you to view directly connected Cisco devices?

A. enable cdp
B. cdp enable
C. cdp run
D. run cdp

Correct Answer: C

Explanation:
CDP is enabled on Cisco routers by default. If you prefer not to use the CDP capability, disable it with the no cdp run command. In order to re-enable CDP, use the cdp run command in global configuration mode. The “cdp enable” command is an interface command, not global.

CISCO CCNA Exam – Q179

Refer to the exhibit.
CISCO CCNA Exam – Q179

According to the routing table, where will the router send a packet destined for 10.1.5.65?

A. 10.1.1.2
B. 10.1.2.2
C. 10.1.3.3
D. 10.1.4.4

Correct Answer: C

Explanation:
The destination IP address 10.1.5.65 belongs to 10.1.5.64/28, 10.1.5.64/29 & 10.1.5.64/27 subnets but the “longest prefix match” algorithm will choose the most specific subnet mask; the prefix “/29″ will be chosen to route the packet. Therefore the next-hop should be 10.1.3.3.