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Identify and correct common network problems at layers 1, 2, 3 and 7 using a layered model approach (8 questions)

QUESTION NO: 1

Part of the TestKing network is shown below:

Study the exhibit shown above. A problem with network connectivity has been observed. It is suspected that the cable connected to switch port Fa0/9 on Switch TestKing1 is disconnected. What would be an effect of this cable being

disconnected?

B. Host TestKingB would not be able to access the server in VLAN9 until the cable is reconnected

C. For less than a minute, Host TestKingB would not be able to access the server in VLAN9. Then normal network function would resume

D. The transfer of files from Host TestKingB to the server in VLAN9 would be significantly slower

E. None of the above

Answer: C Explanation:

Spanning-Tree Protocol (STP) is a Layer 2 protocol that utilizes a special-purpose algorithm to discover physical loops in a network and effect a logical loop-free topology. STP creates a loop-free tree structure consisting of leaves and branches that span the entire Layer 2 network. The actual mechanics of how bridges communicate and how the STP algorithm works will be discussed at length in the following topics. Note that the terms bridge and switch are used interchangeably when discussing STP. In addition, unless otherwise indicated, connections between switches are assumed to be trunks. STP keeps the port either in block or in forward states, when forward port disconnect then within the less then a minute blocked port comes into forward state so packets starts to go through new forward port.

The Spanning Tree Protocol (STP) would identify the best path as well as alternate path to reach in proper destination. In a redundant link, if the primary link fails then the secondary links will automatically start after few minutes. If port Fa0/9 became disconnected, then the packets would be re-routed automatically using the TestkingA-Testking2-TestKing3 path.

QUESTION NO: 2

You are logged into a router and wish to view the layer 3 information about your neighboring Cisco routers. What IOS command gives layer 3 information for of the directly connected router interfaces?

A. show ip links B. show cdp neighbor C. show cdp neighbor detail D. show ip clients

E. show ip route F. None of the above

Answer: C Explanation:

To display detailed information about neighboring devices discovered using Cisco Discovery Protocol (CDP), use theshow cdp neighbors privileged EXEC command. Detail - (Optional) Displays detailed information about a neighbor (or neighbors) including network address, enabled protocols, hold time, and software version.

Incorrect Answers:

A, D. These are invalid commands.

B. The "show cdp neighbor" command, without the "detail" keyword will not display the additional layer 3 protocol information.

E. This will show all routes from all other routers within the domain. We wish to see information from just the direct interface neighbors.

QUESTION NO: 3

A TestKing technician is troubleshooting connectivity problems between two routers that are directly connected through the serial line. The technician notices that the serial line is up but cannot see any neighbors displayed in the output of the show cdp neighbors command.

In which OSI layer is the problem most likely occurring?

A. Physical B. Data link C. Network layer D. Transport layer E. Application layer Answer: B Explanation:

As the question states that serial line is up, it means the problem is not on the Network layer. The administrator cannot see any output by issuing the show cdp neighbors

command. It means that CDP is disabled and CDP is a protocol that runs over Layer2 (the data link layer) on all Cisco routers, bridges, access servers, and switches.

While troubleshooting a network connectivity problem, a TestKing technician observes steady link lights on both the workstation NIC and the switch port to which the workstation is connected. However, when the ping command is issued from the workstation, the output message "Request timed out." is displayed. At which layer of the 7-layer OSI model does the problem most likely exist?

A. The data link layer B. The application layer C. The protocol layer D. The access layer E. The session layer F. The network layer G. None of the above

Answer: F

QUESTION NO: 5

The two connected ports on the switch are not turning orange or green. What would be the most effective steps to troubleshoot this physical layer problem? (Choose three)

A. Ensure that the Ethernet encapsulations match on the interconnected router and switch ports.

B. Ensure that cables A and B are straight-through cables. C. Ensure cable A is plugged into a trunk port.

D. Ensure that switch has power. E. Reboot all of the devices. F. Reseat all cables.

Answer: B, D, F Explanation:

Straight-through cables are used to connect hosts to a switch (or hub) and routers to a switch (or hub). See the table below:

Incorrect Answers:

A: This would mean that there was a layer 2 issue, not layer 1. If the problem was related to the encapsulation, the lights on the switch would indicate layer 1 activity.

C: A trunk port is not required, and again if this was the problem the link lights on the switch would be on.

E: This should only be used as a last resort, as this will affect all users on the switch.

QUESTION NO: 6

Which line from the output of the show ip interface command indicates that there is a Layer 1 problem?

A. Serial0/1 is up, line protocol is down B. Serial0/1 is down, line protocol is down C. Serial0/1 is up, line protocol is up

D. Serial0/1 is administratively down, line protocol is down E. None of the above

Answer: B Explanation:

When the physical interface itself is down, then the problem is related to layer 1. When it is up, but the line protocol is down, then the problem is related to layer 2.

Reference: http://www.cisco.com/univercd/cc/td/doc/cisintwk/itg_v1/tr1915.htm

QUESTION NO: 7

At which layer of the OSI model does the protocol that provides the information displayed by the "show cdp neighbors" command operate?

A. Transport B. Physical C. Application

D. Data link E. Network

Answer: D Explanation:

CDP is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured devices (routers, bridges, access servers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices. With CDP, network management applications can learn the device type and the Simple Network Management Protocol (SNMP) agent address of neighboring devices running lower-layer, transparent protocols.

QUESTION NO: 8

Which three of the protocols below belong to the application layer? (Select three answer choices) A. ARP B. HTTPS C. SMTP D. CDP E. TFTP F. ICMP Answer: B, C, E Explanation:

The application layer is the highest OSI layer, and protocols at this layer are end-user oriented. HTTPS so people can get information on the internet, SMTP so people can manage networks, and TFTP so people can download files.

Incorrect Answers:

A, D, F. ARP, CDP, ICMP are protocols that equipment like routers and switches use to communicate with themselves, and belong to lower levels on the model.

Section 11: Differentiate between LAN/WAN operation and