思科CCNA题目及答案

CCNA-Cisco-Chapter11C11 An electrician has investigated your recent power problems and has suggested that they are caused by oscillation. What is the BEST solution to your problem?Move the network server to another roomReplace UTP with fiber optic cable* Rewire the electrical systemFit commercial surge suppressors2 What is another term that can be used to describe an Intermediate Distribution Frame (IDF)? work area (WA)telecommunications outlet (TO)main cross-connect (MCC)* horizontal cross-connect (HCC)3 Why is fiber optic cable commonly used as a network backbone between campus buildings?It provides a less resistive path for electrical current to flow from one building to anotherIt enhances the signals at the physical layer* It reduces the hazardous effects of electrical potential difference and lightning strikesIt is cheaper and easier to install than copper wire4 Which of the following environmental specifications are recommended for a wiring closet ? Carpeted floor; tiled walls and an inward opening doorWooden floor; brick walls and fluorescent lightingTiled floor; internal power outlets and a dropped ceiling* Raised floor; wood covered walls and an internal light switch5 What is one of the most significant causes of oscillatory noise problems on a power circuit? ??? Long wiring runsSchool photocopiersLocating power cables in elevator shaftsAir conditioners cycling on and off6 What device is best used to minimize the effects of power line sags and brownouts?A primary protection deviceA surge suppressorAn optical isolator* An uninterruptible power supply7 What causes Electrostatic Discharge (ESD)?Long power linesFaulty electrical equipment* An accumulation of static electricityAn increase in atmospheric humidity8 Which of the following problems is caused by too high a humidity level in a wiring closet? Signal degradation* Copper wire corrosionInsulation failurePower surges9 What is the ideal room temperature and relative humidity at which a wiring closet should bemaintained?* 21 degrees Celsius / 45 % relative humidity21 degrees Fahrenheit / 45 % relative humidity45 degrees Celsius / 21 % relative humidity45 degrees Fahrenheit / 21 % relative humidity10 What is the maximum length specified for 62.5/125µm multimode optical fiber run between the MDF and IDF?90 m800 m2000 m* 3000 m11 What are the three components that make up an uninterruptible power supply?* A battery, inverter and battery chargerA MOV, capacitor and diodeA generator, changeover circuit and server softwareA circuit breaker, fuse and battery12 Where does the horizontal cable extend?From the main distribution frame in the wiring closet to the vertical cross connect in the intermediate distribution frameFrom the telecommunications outlet in the work area to the horizontal cross-connect in the telecommunications closet* From the patch panel in the point of presence to the backbone connection in the customer premises equipmentFrom the telecommunications outlet in the wiring closet to the conduit in the intermediate distribution frame13 Which statement BEST describes the current flow in an electrical circuit with a DC source?* It is constant over timeIt varies over timeIt increases with timeIt decreases with time14 Why are exposed metal components normally connected to the ground, or earth, pin of a power outlet?The connection is needed to increase the resistance of the circuit to ground* If an electrical fault occurs in the equipment, the connection will reduce the chance of shock Connecting the metal to ground makes it act like an insulatorThe ground connection can act as an alternative path for controlled current flow if the neutral wire is disconnected15 What is the term used to describe a problem in an electrical system between the hot, or live, wire and the neutral wire?An isolated mode problemA ground fault problem* A common mode problemA normal mode problem16 What function does an electrical insulator perform?It completes the circuit, allowing current to flowIt reduces the resistance in an electrical circuitIt allows a short circuit to be present* It prevents uncontrolled current flow17 What is an alternative name for backbone cabling?Horizontal cabling* Vertical cablingMain cablingTrunk cabling18 Why can digital electronic equipment, such as a computer, malfunction if subjected to excessive power line noise?Logic gates are unable to correctly distinguish the noise polarityThe noise enhances the digital signal edgesThe noise replaces the digital signal* Logic gates are unable to correctly distinguish between a one and a zero19 A potential wiring closet has been identified in a building with a floor area of 930 sq. m. The distance from this closet to the furthest workstation is 127 m. How many ADDITIONAL wiring closets would need to be installed?* 012820 Why is copper considered a good conductor of electricity?* It offers a path of least resistance to current flowIt is easily formed into wiresIt is cheaper than other metalsIt reduces power line noise21 In a controlled electrical circuit, which path do electrons normally follow?From the positively charged source to ground* From the negatively charged source to a positively charged sourceFrom the more positively charged source to the less positively charged sourceFrom the negatively charged source to ground22 What is the purpose of providing a ground, or earth, connection on a wall power outlet?To reduce the resistance in the electrical circuitTo link the neutral wire to ground* To allow fault currents to flow to groundTo complete the circuit for normal current to flow23 What is a possible problem associated with multiple building grounds?They are often at the same potential with respect to each otherThey do not allow electrical current to flow between the buildingsSeparate protective devices are needed at each building* They may present a shock hazard due to different potentials24 What features should be considered when assessing a potential wiring closet?It should be secure and situated on the first (ground) floor???? It should be secure and close to the POPIt should be within 150 m of the MDF and close to an entranceIt should be an internal room and close to the electrical supply distributionC21. Which statements correctly identify the role of intermediary devices in the network? (Choose three.)determine pathways for datainitiate data communicationsretime and retransmit data signalsoriginate the flow of datamanage data flowsfinal termination point for data flow2. Select the statements that are correct concerning network protocols. (Choose three.) define the structure of layer specific PDU'sdictate how to accomplish layer functionsoutline the functions necessary for communications between layerslimit the need for hardware compatibilityrequire layer dependent encapsulationseliminate standardization among vendors3. What are two functions of encapsulation? (Choose two.)tracks delay between end devicesenables consistent network paths for communicationallows modification of the original data before transmissionidentifies pieces of data as part of the same communicationensures that data pieces can be directed to the correct receiving end device4. What is a primary function of the trailer information added by the data link layer encapsulation?supports error detectionensures ordered arrival of dataprovides delivery to correct destinationidentifies the devices on the local networkassists intermediary devices with processing and path selection5. Which statements correctly identify the role of intermediary devices in the network? (Choose three.)determine pathways for datainitiate data communicationsretime and retransmit data signalsoriginate the flow of datamanage data flowsfinal termination point for data flow6. What is a PDU?corruption of a frame during transmissiondata reassembled at the destinationretransmitted packets due to lost communicationa layer specific encapsulation7. Which characteristic correctly refers to end devices in a network?manage data flowsoriginate data flowretime and retransmit data signalsdetermine pathways for data10. Which three statements best describe a Local Area Network (LAN)? (Choose three.)A LAN is usually in a single geographical area.The network is administered by a single organization.The connection between segments in the LAN is usually through a leased connection. The security and access control of the network are controlled by a service provider.A LAN provides network services and access to applications for users within a common organization.Each end of the network is generally connected to a Telecommunication Service Provider (TSP).12. What is the primary purpose of Layer 4 port assignment?to identify devices on the local mediato identify the hops between source and destinationto identify to the intermediary devices the best path through the networkto identify the source and destination end devices that are communicatingto identify the processes or services that are communicating within the end devices13. What device is considered an intermediary device?file serverIP phonelaptopprinterswitch16. Which layer encapsulates the segment into packets?physicaldata linknetworktransport17. What can be identified by examining the network layer header?the destination device on the local mediathe destination host addressthe bits that will be transferred over the mediathe source application or process creating the data18. What is the purpose of the TCP/IP Network Access layer?path determination and packet switchingdata presentationreliability, flow control, and error detectionnetwork media controlthe division of segments into packets19. During the encapsulation process, what occurs at the data link layer?No address is added.The logical address is added.The physical address is added.The process port number is added.21. What is the proper order of the layers of the OSI model from the highest layer to the lowest layer?4physical, network, application, data link, presentation, session, transport application, physical, session, transport, network, data link, presentation application, presentation, physical, session, data link, transport, network application, presentation, session, transport, network, data link, physical presentation, data link, session, transport, network, physical, application22. Which two layers of the OSI model have the same functions as the TCP/IP model Network Access Layer? (Choose two.)34NetworkTransportPhysicalData LinkSessionC31 How does the application layer on a server usually process multiple client request for services?ceases all connections to the servicedenies multiple connections to a single daemonsuspends the current connection to allow the new connectionuses support from lower layer functions to distinguish between connections to the service2 A small home network has been installed to interconnect three computers together for gaming and file sharing. What two properties represent this network type? (Choose two.)User accounts are centralized.Security is difficult to enforce.Specialized operating system software is required.File permissions are controlled by a single computer.A computer that responds to a file sharing request is functioning as a server.3 What is the purpose of resource records in DNS?temporarily holds resolved entriesused by the server to resolve namessent by the client to during a querypasses authentication information between the server and client4 A network administrator is designing a network for a new branch office of twenty-five users. What are the advantages of using a client-server model? (Choose two.)centralized administrationdoes not require specialized softwaresecurity is easier to enforcelower cost implementationprovides a single point of failure5 What are three properties of peer-to-peer applications? (Choose three.)acts as both a client and server within the same communicationrequires centralized account administrationhybrid mode includes a centralized directory of filescan be used in client-server networksrequires a direct physical connection between devicescentralized authentication is required6 As compared to SSH, what is the primary disadvantage of telnet?not widely availabledoes not support encryptionconsumes more network bandwidthdoes not support authentication7 What is the automated service that matches resource names with the required IP address?HTTPSSHFQDNDNSTelnetSMTP8 What application layer protocol describes the services that are used for file sharing in Microsoft networks?DHCPDNSSMBSMTPTelnet9 Which two protocols are used to control the transfer of web resources from a web server to a client browser? (Choose two.)ASPFTPHTMLHTTPHTTPSIP10 What three protocols operate at the Application layer of the OSI model? (Choose three.)ARPDNSPPPSMTPPOPICMP11 Which layer of the OSI model supplies services that allow user to interface with the network?physicalsessionnetworkpresentationapplicationtransport12 Which email components are used to forward mail between servers? (Choose two.) MDAIMAPMTAPOPSMTPMUA13 What are two forms of application layer software? (Choose two.)applicationsdialogsrequestsservicessyntax14 Which statements are correct concerning the role of the MTA in handling email? (Choose three.)routes email to the MDA on other serversreceives email from the client's MUAreceives email via the POP3 protocolpasses email to the MDA for final deliveryuses SMTP to route email between serversdelivers email to clients via the POP3 protocol15 What are two characteristics of clients in data networks? (Choose two.)use daemonsinitiate data exchangesare repositories of datamay upload data to serverslisten for requests from servers16 What is the role of the OSI application layer?provides segmentation of dataprovides encryption and conversion of dataprovides the interface between the applications on either end of the network provides control of all the data flowing between the source and destination devices 17 Which application layer protocols correctly match a corresponding function? (Choose two.)DNS dynamically allocates IP addresses to hostsHTTP transfers data from a web server to a clientPOP delivers email from the client to the server email serverSMTP supports file sharingTelnet provides a virtual connection for remote access19 What are two characteristics of peer-to-peer networks? (Choose two.) scalableone way data flowdecentralized resourcescentralized user accountsresource sharing without a dedicated server20 What application layer protocol is commonly used to support for file transfers between a client and a server?HTMLHTTPFTPTelnetC42. With TCP/IP data encapsulation, which range of port numbers identifies all well-known applications?0 to 255256 to 10220 to 10231024 to 204749153 to 655353. Why are port numbers included in the TCP header of a segment?to indicate the correct router interface that should be used to forward a segmentto identify which switch ports should receive or forward the segmentto determine which Layer 3 protocol should be used to encapsulate the datato enable a receiving host to forward the data to the appropriate applicationto allow the receiving host to assemble the packet in the proper order4. Which OSI model layer is responsible for regulating the flow of information from source to destination, reliably and accurately?applicationpresentationsessiontransportnetwork6. Why is flow control used for TCP data transfer?to synchronize equipment speed for sent datato synchronize and order sequence numbers so data is sent in complete numerical orderto prevent the receiver from being overwhelmed by incoming datato synchronize window size on the serverto simplify data transfer to multiple hosts7. Which two options represent Layer 4 addressing? (Choose two.)identifies the destination networkidentifies source and destination hostsidentifies the communicating applicationsidentifies multiple conversations between the hostsidentifies the devices communicating over the local media10. What is dynamically selected by the source host when forwarding data? destination logical addresssource physical addressdefault gateway addresssource port11. What are two features of the User Datagram Protocol (UDP)? (Choose two.) flow controllow overheadconnectionlessconnection-orientedsequence and acknowledgements12. What mechanism is used by TCP to provide flow control as segments travel from source to destination?sequence numberssession establishmentwindow sizeacknowledgments13. Which transport layer protocol provides low overhead and would be used for applications which do not require reliable data delivery?TCPIPUDPHTTPDNS14. Which information is found in both the TCP and UDP header information? sequencingflow controlacknowledgmentssource and destination port15. Which three features allow TCP to reliably and accurately track the transmission of data from source to destination? (Choose three.)flow controlurgent pointerbest effort deliverysession establishmentconnectionless servicesnumbering and sequencing16. During a TCP communication session, if the packets arrive to the destination out of order, what will happen to the original message?The packets will not be delivered.The packets will be retransmitted from the source.The packets will be delivered and reassembled at the destination.The packets will be delivered and not reassembled at the destination.17. Which is an important characteristic of UDP?acknowledgement of data deliveryminimal delays in data deliveryhigh reliability of data deliverysame order data delivery18. After a web browser makes a request to a web server that is listening to the standard port, what will be the source port number in the TCP header of the response from the server?1353801024172819. Which event occurs during the transport layer three-way handshake?The two applications exchange data.TCP initializes the sequence numbers for the sessions.UDP establishes the maximum number of bytes to be sent.The server acknowledges the bytes of data received from the client.C51 What is the purpose of a default gateway?physically connects a computer to a networkprovides a permanent address to a computeridentifies the network to which a computer is connectedidentifies the logical address of a networked computer and uniquely identifies it to the rest of the networkidentifies the device that allows local network computers to communicate with devices on other networks2 What type of routing uses information that is manually entered into the routing table?dynamicinteriorstaticstandard4 Which IP packet field will prevent endless loops?type-of-serviceidentificationflagstime-to-liveheader checksum6 What is a component of a routing table entry?the MAC address of the interface of the routerthe destination Layer 4 port numberthe destination host addressthe next-hop address7 In an IPv4 environment, what information is used by the router to forward data packets from one interface of a router to another?destination network addresssource network addresssource MAC addresswell known port destination address8 What information is added during encapsulation at OSI Layer 3?source and destination MACsource and destination application protocolsource and destination port numbersource and destination IP address9 If the default gateway is configured incorrectly on the host, what is the impact on communications?The host is unable to communicate on the local network.The host can communicate with other hosts on the local network, but is unable to communicate with hosts on remote networks.The host can communicate with other hosts on remote networks, but is unable to communicate with hosts on the local network.There is no impact on communications.10 In a connectionless system, which of the following is correct?The destination is contacted before a packet is sent.The destination is not contacted before a packet is sent.The destination sends an acknowledgement to the source that indicates the packet was received.The destination sends an acknowledgement to the source that requests the next packet to be sent.11 Which portion of the network layer address does a router use to forward packets? host portionbroadcast addressnetwork portiongateway address13 When the destination network is not listed in the routing table of a Cisco router, what are two possible actions that the router might take? (Choose two.)The router sends an ARP request to determine the required next hop address.The router discards the packet.The router forwards the packet toward the next hop indicated in the ARP table.The router forwards the packet to the interface indicated by the source address.The router forwards the packet out the interface indicated by the default route entry.14 What are three common problems with a large network? (Choose three.)too few broadcastsperformance degradationsecurity issueslimited management responsibilityhost identificationprotocol compatibility15 Which three statements are true about routes and their use? (Choose three.)If no route to the destination network is found, the packet is returned to the previous router.If the destination network is directly connected, the router forwards the packet to the destination host.If multiple network entries exist for the destination network, the most general route is used to forward the packet.If no route exists for the destination network and a default route is present, the packet is forwarded to the next-hop router.If the originating host has a default gateway configured, the packet for a remote network can be forwarded using that route.If a host does not have a route manually configured for the destination network, the host will drop the packet.16 Which intermediary devices could be used to implement security between networks? (Choose two.)routerhubswitchfirewallaccess pointbridge19 What are the key factors to consider when grouping hosts into a common network? (Choose three.)gatewayspurposephysical addressingsoftware versiongeographic locationownership20 What two characteristics are commonly associated with dynamic routing protocols? (Choose two.)require no device configurationprovide routers with up-to-date routing tablesrequire less processing power than static routes requireconsume bandwidth to exchange route informationprevent manual configuration and maintenance of the routing table21. What statement describes the purpose of a default route?A host uses a default route to transfer data to another host on the same network segment.A host uses a default route to forward data to the local switch as the next hop to all destinations.A host uses a default route to identify the Layer 2 address of an end device on the local network.A host uses a default route to transfer data to a host outside the local network when no other route to the destination exists.C62 Which IPv4 subnetted addresses represent valid host addresses? (Choose three.) 172.16.4.127 /26172.16.4.155 /26172.16.4.193 /26172.16.4.95 /27172.16.4.159 /27172.16.4.207 /273 Which statements are true regarding IP addressing? (Choose two.)NAT translates public addresses to private addresses destined for the Internet.Only one company is allowed to use a specific private network address space.Private addresses are blocked from public Internet by router.Network 172.32.0.0 is part of the private address space.IP address 127.0.0.1 can be used for a host to direct traffic to itself.4 Which process do routers use to determine the subnet network address based upon a given IP address and subnet mask?binary addinghexadecimal andingbinary divisionbinary multiplicationbinary ANDing5 What is the network address of the host 172.25.67.99 /23 in binary?10101100. 00011001.01000011.0000000010101100. 00011001.01000011.1111111110101100. 00011001.01000010.0000000010101100. 00011001.01000010.0110001110101100. 00010001.01000011. 0110001010101100. 00011001.00000000.000000006 What subnet mask would a network administrator assign to a network address of 172.30.1.0 if it were possible to have up to 254 hosts?255.255.0.0255.255.255.0255.255.254.0255.255.248.07 Which three IP addresses are private? (Choose three.)172.168.33.110.35.66.70192.168.99.5172.18.88.90192.33.55.89172.35.16.58 Given the IP address and subnet mask of 172.16.134.64 255.255.255.224, which of the following would describe this address?This is a useable host address.This is a broadcast address.This is a network address.This is not a valid address.11 Which of the following network devices are recommended to be assigned static IP addresses? (Choose three.)LAN workstationsserversnetwork printersroutersremote workstationslaptops12 Which of the following are features of IPv6? (Choose three.)larger address spacefaster routing protocolsdata types and classes of serviceauthentication and encryptionimproved host naming conventionssame addressing scheme as IPv413 A router interface has been assigned an IP address of 172.16.192.166 with a mask of 255.255.255.248. To which subnet does the IP address belong?172.16.0.0172.16.192.0172.16.192.128172.16.192.160172.16.192.168172.16.192.17614 What two things will happen if a router receives an ICMP packet which has a TTL value of 1 and the destination host is several hops away? (Choose two.)The router will discard the packet.The router will decrement the TTL value and forward the packet to the next router on the path to the destination host.The router will send a time exceeded message to the source host.The router will increment the TTL value and forward the packet to the next router on the path to the destination host.The router will send an ICMP Redirect Message to the source host.16 How many bits make up an IPv4 address?12864483217 What is the primary reason for development of IPv6?securityheader format simplificationexpanded addressing capabilitiesaddressing simplification18 What three facts are true about the network portion of an IPv4 address? (Choose three.)identifies an individual deviceis identical for all hosts in a broadcast domainis altered as packet is forwardedvaries in lengthis used to forward packetsuses flat addressing19 What is a group of hosts called that have identical bit patterns in the high order bits of their addresses?an interneta networkan octeta radixC71 What is a function of the data link layer?。