CCNA第二学期练习答案chapter3
计算机网络课后答案第三章
第三章 数据链路层习题3-02 数据链路层中的链路控制包括哪些功能？答：数据链路层中的链路控制功能有：（1）链路管理。
（2）帧定界。
（3）流量控制。
（4）差错控制。
（5）将数据和控制信息区分开。
（6）透明传输。
（7）寻址。
习题3-03考察停止等待协议算法。
在接收结点，当执行步骤（4）时，若将“否则转到（7）”改为“否则转到（8）”，将产生什么结果？答：“否则”是指发送方发送的帧的N （S ）和接收方的状态变量V （R ）不同。
表明发送方没有收到接收方发出的ACK ，于是重传上次的帧。
若“转到（8）”，则接收方要发送NAK 。
发送方继续重传上次的帧，一直这样下去。
习题3-06 信道速率为4kb/s 。
采用停止等待协议。
传播时延ms t p 20=,确认帧长度和处理时间均可忽略。
问帧长为多少才能使信道利用率达到至少50%。
解：根据下图所示停等协议中的时间关系：在确认帧长度和处理时间均可忽略的情况下，要使信道利用率达到至少50%必须使数据帧的发送时间等于2倍的单程传播时延。
即：p f t t 2= 已知：C l t f f =，其中C 为信道容量，或信道速率。
f l 为帧长（以比特为单位）。
所以得帧长16004.040002=⨯=⨯≥⨯=p f f t C t C l bit习题3-09试证明：当用n 个比特进行编号时，若接收窗口的大小为1，则只有在发送窗口的大小WT ≤2n-1时，连续ARQ 协议才能正确运行。
答：（1）显然 WT 内不可能有重复编号的帧，所以WT ≤2n 。
设WT=2n ；（2）注意以下情况：发送窗口：只有当收到对一个帧的确认，才会向前滑动一个帧的位置；接收窗口：只有收到一个序号正确的帧，才会向前滑动一个帧的位置，且同时向发送端发送对该帧的确认。
显然只有接收窗口向前滑动时，发送端口才有可能向前滑动。
发送端若没有收到该确认，发送窗口就不能滑动。
（3）为讨论方便，取n=3。
并考虑当接收窗口位于0时，发送窗口的两个极端状态。
CCNA2 题库
CCNA 2 - Chapter 11What is one advantage of using the cut-through switching method instead of the store-and-forward switching method?has a positive impact on bandwidth by dropping most of the invalid framesmakes a fast forwarding decision based on the source MAC address of the framehas a lower latency appropriate for high-performance computing applications*provides the flexibility to support any mix of Ethernet speeds2A network designer must provide a rationale to a customer for a design which will move an enterprise from a flat network topology to a hierarchical network topology. Which two features of the hierarchical design make it the better choice? (Choose two.)reduced cost for equipment and user trainingless required equipment to provide the same performance levelssimpler deployment for additional switch equipment*easier to provide redundant links to ensure higher availability*lower bandwidth requirements3What are two advantages of modular switches over fixed-configuration switches? (Choose two.)availability of multiple ports for bandwidth aggregationlower forwarding ratesneed for fewer power outlets*lower cost per switchincreased scalability*4Refer to the exhibit. Consider that the main power has just been restored. PC1 asks the DHCP server for IPv4 addressing. The DHCP server sends it an IPv4 address. While PC2 is still booting up, PC3 issues a broadcast IPv4 DHCP request. To which port will SW1 forward this request?to Fa0/1, Fa0/2, and Fa0/4 onlyto Fa0/1, Fa0/2, Fa0/3, and Fa0/4to Fa0/1 and Fa0/2 onlyto Fa0/1, Fa0/2, and Fa0/3 only*to Fa0/1 only5What is one function of a Layer 2 switch?forwards data based on logical addressinglearns the port assigned to a host by examining the destination MAC addressduplicates the electrical signal of each frame to every portdetermines which interface is used to forward a frame based on the destination MAC address*6Refer to the exhibit. Fill in the blank.There are ” 12” collision domains in the topology.7What is a collapsed core in a network design?a combination of the functionality of the access, distribution, and core layersa combination of the functionality of the access and core layersa combination of the functionality of the distribution and core layers*a combination of the functionality of the access and distribution layers 8What are two reasons a network administrator would segment a network with a Layer 2 switch? (Choose two.)to enhance user bandwidth*to eliminate virtual circuitsto create more broadcast domainsto isolate traffic between segments*to isolate ARP request messages from the rest of the networkto create fewer collision domains9Refer to the exhibit.How is a frame sent from PCA forwarded to PCC if the MAC address table on switch SW1 is empty?SW1 forwards the frame directly to SW2. SW2 floods the frame to all ports connected to SW2, excluding the port through which the frame entered the switch.SW1 floods the frame on all ports on the switch, excluding the interconnected port to switch SW2 and the port through which the frame entered the switch.SW1 floods the frame on all ports on SW1, excluding the port through which the frame entered the switch.*SW1 drops the frame because it does not know the destination MAC address.10Place the options in the following order:[+] appropriate for high performance computing applications[+] forwarding process can begin after receiving the destination address [+] may forward invalid frames[#] error checking before forwarding[#] forwarding process only begin after receiving the entire frame [#] only forward valid frames[+] Order does not matter within this group.[#] Order does not matter within this group.11What is a basic function of the Cisco Borderless Architecture distribution layer?aggregating Layer 3 routing boundaries*aggregating all the campus blocksacting as a backboneproviding access to the user12ABC, Inc. has about fifty hosts in one LAN. The administrator would like to increase the throughput of that LAN. Which device will increase the number of collision domains and thereby increase the throughput of the LAN?hubhostNICswitch*13What does the term “port density” represent for an Ethernet switch?the numbers of hosts that are connected to each switch portthe speed of each portthe memory space that is allocated to each switch portthe number of available ports*14Which type of transmission does a switch use when the destination MAC address is not contained in the MAC address table?anycastunicastbroadcast*multicast15What is a basic function of the Cisco Borderless Architecture access layer?aggregates Layer 3 routing boundariesprovides high availabilityaggregates Layer 2 broadcast domainsprovides access to the user*16What information is added to the switch table from incoming frames?source MAC address and incoming port number*destination MAC address and incoming port numberdestination IP address and incoming port numbersource IP address and incoming port number17Fill in the blank.A “converged” network is one that uses the same infrastructure to carry voice, data, and video signals.18An administrator purchases new Cisco switches that have a feature called StackPower. What is the purpose of this feature?It enables many switches to be connected with a special fiber-optic power cable to provide higher bandwidth.It enables the sharing of power among multiple stackable switches.*It enables many switches to be connected to increase port density.It enables many switches to be physically stacked in an equipment rack.It enables AC power for a switch to be provided from a powered patch panel.19Which switch form factor should be used when large port density, fault tolerance, and low price are important factors?fixed-configuration switchmodular switchstackable switch*rackable 1U switch20Refer to the exhibit. Fill in the blank.There are ” 5 ”CCNA 2 - Chapter 2Posted by beotron at 8:59 PM1. A static route that points to the next hop IP will have what administrative distance and metric in the routing table?• administrative distance of 0 and metric of 0• administrative distance of 0 and metric of 1• administrative distance of 1 and metric of 0• administrative distance of 1 and metric of 12. What address can be used to summarize networks 172.16.1.0/24, 172.16.2.0/24, 172.16.3.0/24, and 172.16.4.0/24?• 172.16.0.0/21• 172.16.1.0/22• 172.16.0.0 255.255.255.248• 172.16.0.0 255.255.252.03. The routers in the diagram use the subnet assignments shown. What is the most efficient route summary that can be configured on Router3 to advertise the internal networks to the cloud?• 192.1.1.0/26 and 192.1.1.64/27• 192.1.1.128/25• 192.1.1.0/23 and 192.1.1.64/23• 192.1.1.0/24• 192.1.1.0/25• 192.1.1.0/24 and 192.1.1.64/244. Refer to the exhibit. What is the significance of the /8 in the route to the 10.0.0.0 network?• It indicates that there are 8 hops between this router and the 10.0.0.0 network.• It represents the time, in milliseconds, it takes for a ping to reply when sent to the 10.0.0.0 network.• It indicates that there are 8 subnets in the destination network to which the router can forward packets.• It indicates the number of consecutive bits, from the left, in the destination IP address of a packet that must match 10.0.0.0 to use that route.5. Refer to the exhibit. How will packets destined to the 172.16.0.0 network be forwarded?• Router1 will perform recursive lookup and packet will exit S0/0.• Router1 will perform recursive lookup and packet will exit S0/1.• There is no matching interface associated with network 172.16.0.0 so packets will be dropped.• There is no matching interface associated with network 172.16.0.0 so packets will take gateway of last resort and exit out S0/2.6. A network administrator enters the following command into Router1: ip route 192.168.0.0255.255.255.0 S0/1/0. Router1 then receives a packet that is destined for 192.168.0.22/24. After finding the recently configured static route in the routing table, what does Router1 do next to process the packet? • drops the packet because the destination host is not listed in the routing table• looks up the MAC address of the S0/1/0 interface to determine the destination MAC address of the new frame• performs a recursive lookup for the IP address of the S0/1/0 interface before forwarding the packet• encapsulates the packet into a frame for the WAN link and forwards the packet out the S0/1/0 interface7. Refer to the exhibit. Given the output in the exhibit, how would a clock rate be determined for this link? • The rate would be negotiated by both routers.• A rate would not be selected due to the DCE/DTE connection mismatch.• The rate configured on the DTE determines the clock rate.• The rate configured on the DCE determines the clock rate.8. Refer to the exhibit. Which set of commands will configure static routes that will allow the WinterPark and the Altamonte routers to deliver packets from each LAN and direct all other traffic to the Internet? • WinterPark(config)# ip route 0.0.0.0 0.0.0.0 192.168.146.1Altamonte(config)# ip route 10.0.234.0 255.255.255.0 192.168.146.2Altamonte(config)# ip route 0.0.0.0 0.0.0.0 s0/1• WinterPark(config)# ip route 0.0.0.0 0.0.0.0 192.168.146.1Altamonte(config)# ip route 10.0.234.0 255.255.255.0 192.168.146.2Altamonte(config)# ip route 198.18.222.0 255.255.255.255 s0/1• WinterPark(config)# ip route 172.191.67.0 255.255.255.0 192.168.146.1• WinterPark(config)# ip route 0.0.0.0 0.0.0.0 192.168.146.1Altamonte(config)# ip route 10.0.234.0 255.255.255.0 192.168.146.2• WinterPark(config)# ip route 172.191.67.0 255.255.255.0 192.168.146.1Altamonte(config)# ip route 10.0.234.0 255.255.255.0 192.168.146.2Altamonte(config)# ip route 0.0.0.0 0.0.0.0 s0/09. Hosts on two separate subnets cannot communicate. The network administrator suspects a missing route in one of the routing tables. Which three commands can be used to help troubleshoot Layer 3 connectivity issues? (Choose three.)• ping• show arp• traceroute• show ip route• show interface• show cdp neighbor d etail10. Refer to the exhibit. A company network engineer is assigned to establish connectivity between the two Ethernet networks so that hosts on the 10.1.1.0/24 subnet can contact hosts on the 10.1.2.0/24 subnet. The engineer has been told to use only static routing for these company routers. Which set of commands will establish connectivity between the two Ethernet networks?• R1(config)# ip route 10.1.2.0 255.255.255.0 192.168.0.1R2(config)# ip route 10.1.1.0 255.255.255.0 192.168.0.2• R1(config)# ip route 10.1.2.0 255.255.255.0 192.168.0.2R2(config)# ip route 10.1.1.0 255.255.255.0 192.168.0.1• R1(config)# ip route 10.1.1.0 255.255.255.0 192.168.0.2R2(config)# ip route 10.1.2.0 255.255.255.0 192.168.0.1• R1(config)# ip route 10.1.1.0 255.255.255.0 192.168.0.1R2(config)# ip route 10.1.2.0 255.255.255.0 192.168.0.2• R1(config)# ip route 0.0.0.0 0.0.0.0 10.1.2.1R2(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.111. Which of the following are displayed by the Router# show cdp neighbors command? (Choose three.) • load• platform• reliability• holdtime• local interface12. Refer to the exhibit. What two commands are required to provide connectivity between the192.168.1.0 and 10.0.0.0 networks without requiring recursive lookup? (Choose two.)• A(config)# ip route 10.0.0.0 255.0.0.0 s 0/1/0• A(config)# ip route 10.0.0.0 255.0.0.0 172.16.40.2• A (config)# ip route 10.0.0.0 255.0.0.0 s 0/0/0• B(config)# ip route 192.168.1.0 255.255.255.0 s 0/0/0• B (config)# ip route 192.168.1.0 255.255.255.0 172.16.40.1• B(config)# ip route 192.168.1.0 255.255.255.0 s 0/1/013. Refer to the exhibit. What two commands will change the next-hop address for the 10.0.0.0/8 network from 172.16.40.2 to 192.168.1.2? (Choose two.)• A(config)# no network 10.0.0.0 255.0.0.0 172.16.40.2• A(config)# no ip address 10.0.0.1 255.0.0.0 172.16.40.2• A(config)# no ip route 10.0.0.0 255.0.0.0 172.16.40.2• A(config)# ip route 10.0.0.0 255.0.0.0 s0/0/0• A(config)# ip route 10.0.0.0 255.0.0.0 192.168.1.214. What happens to a static route entry in a routing table when the outgoing interface is not available? • The route is removed from the table.• The router polls neighbors for a replacement route.• The route remains in the table because it was defined as static.• The router redirects the static route to compensate for the loss of the next hop device.15. A router has one static route to each destination network. Which two scenarios would require an administrator to alter the static routes that are configured on that router? (Choose two.)• The destination network no longer exists.• The destination network is moved to a different interface on the same router.• The path between the source and destination is upgraded with a higher bandwidth link.• A topology change occurs where the exi sting next-hop address or exit interface is not accessible.• The remote destination network interface has to be down for 15 minutes of maintenance.16. Why is it advisable to enter a next-hop IP address when creating a static route whose exit interface is an Ethernet network?• Adding the next-hop address eliminates the need for the router to do any lookups in the routing table before forwarding a packet.• In a multi-access network, the router cannot determine the next-hop MAC address for the Ethernet frame without a next-hop address.• Using a next-hop address in a static route provides a route with a lower metric.• In multi-access networks, using a next-hop address in a static route makes that route a candidate default route.17. The output of the Router# show interfaces serial 0/1 command displays the following:• Serial0/1 is up, line protocol is down.• What is the most likely cause for the line protocol being down?• Serial0/1 is shutdown.• There is no cable connecting the routers.• The remote rout er is using serial 0/0.• No clock rate has been set.18. Refer to the exhibit. Which static route should be configured on Router1 so that host A will be able to reach host B on the 172.16.0.0 network?• ip route 192.168.0.0 172.16.0.0 255.255.0.0• ip rou te 172.16.0.0 255.255.0.0 192.168.0.1• ip route 172.16.0.0 255.255.0.0 S0/0/1• ip route 172.16.0.0 255.255.0.0 S0/0/019. What two devices are responsible for converting the data from the WAN service provider into a form acceptable by the router? (Choose two).• the serial port of the router• a modem• a switch• the ethernet port of the router• a CSU/DSU device• a DTE device20. Which of the following is true regarding CDP and the graphic shown?• CDP running on Router D will gather information about routers A, B, C, and E.• By default, Router A will receive CDP advertisements from routers B and C.• If routers D and E are running different routing protocols, they will not exchange CDP information.• Router E can use CDP to identify the IOS running on Router B.21. Which two statements describe functions or characteristics of CDP? (Choose two.)• It starts up automatically and allows the device to detect directly connected neighbor devices that use CDP.• It operates at the network layer and allows two systems to learn about each other.• It creates a topology map of the entire network.• It allows systems to learn about each other even if different network layer protocols are configured.• It forwards advertisements about routes for faster convergence.22. Which piece of information is available from examining the output of the command show ip interface brief?• Interface speed and duplex• Interface MTU• Errors• Interface MAC address• Interface IP addressCCNA 2 - Chapter 31A network administrator is determining the best placement of VLAN trunklinks. Which two types of point-to-point connections utilize VLAN trunking? (Choose two.)between two switches that share a common VLANbetween a switch and a server that has an 802.1Q NIC*between a switch and a client PCbetween a switch and a network printerbetween two switches that utilize multiple VLANs*2What happens to a port that is associated with VLAN 10 when the administrator deletes VLAN 10 from the switch?The port automatically associates itself with the native VLAN. The port creates the VLAN again.The port goes back to the default VLAN.The port becomes inactive.*3Refer to the exhibit. Interface Fa0/1 is connected to a PC. Fa0/2 is a trunk link to another switch. All other ports are unused. Which security best practice did the administrator forget to configure?Configure all unused ports to a ‘black-hole’ VLAN that is not used f or anything on the network.Disable autonegotiation and set ports to either static access or static trunk.Change the native VLAN to a fixed VLAN that is distinct from all user VLANs and to a VLAN number that is not VLAN 1.All user ports are associated with VLANs distinct from VLAN 1 and distinct from the ‘black-hole’ VLAN.*4Which command is used to remove only VLAN 20 from a switch?no switchport access vlan 20delete flash:vlan.datno vlan 20*delete vlan.dat5A Cisco Catalyst switch has been added to support the use of multiple VLANs as part of an enterprise network. The network technician finds it necessary to clear all VLAN information from the switch in order to incorporate a new network design. What should the technician do to accomplish this task?Erase the startup configuration and reboot the switch.Erase the running configuration and reboot the switch.Delete the startup configuration and the vlan.dat file in the flash memory of the switch and reboot the switch.*Delete the IP address that is assigned to the management VLAN and reboot the switch.6What is the effect of issuing a switchport access vlan 20 command on the Fa0/18 port of a switch that does not have this VLAN in the VLAN database?VLAN 20 will be created automatically.*The command will have no effect on the switch.Port Fa0/18 will be shut down.An error stating that VLAN 20 does not exist will be displayed and VLAN 20 is not created.Which command displays the encapsulation type, the voice VLAN ID, and the access mode VLAN for the Fa0/1 interface?show mac address-table interface Fa0/1show interfaces Fa0/1 switchport*show interfaces trunkshow vlan brief8Place the options in the following order:- not scored -dynamic autononegotiatedynamic desirabletrunk9Port Fa0/11 on a switch is assigned to VLAN 30. If the command no switchport access vlan 30 is entered on the Fa0/11 interface, what will happen?Port Fa0/11 will be returned to VLAN 1.*VLAN 30 will be deleted.An error message would be displayed.Port Fa0/11 will be shutdown.What must the network administrator do to remove Fast Ethernet port fa0/1 from VLAN 2 and assign it to VLAN 3?Enter the no vlan 2 and the vlan 3 commands in global configuration mode. Enter the switchport trunk native vlan 3 command in interface configuration mode.Enter the switchport access vlan 3 command in interface configuration mode.*Enter the no shutdown in interface configuration mode to return it to the default configuration and then configure the port for VLAN 3.11Which two Layer 2 security best practices would help prevent VLAN hopping attacks? (Choose two.)Disable DTP autonegotiation on end-user ports.*Change the management VLAN to a distinct VLAN that is not accessible by regular users.Statically configure all ports that connect to end-user host devices to be in trunk mode.Change the native VLAN number to one that is distinct from all user VLANs and is not VLAN 1.*Use SSH for all remote management access.12In a basic VLAN hopping attack, which switch feature do attackers take advantage of?automatic encapsulation negotiationthe default automatic trunking configuration*an open Telnet connectionforwarding of broadcasts13A Cisco switch currently allows traffic tagged with VLANs 10 and 20 across trunk port Fa0/5. What is the effect of issuing a switchport trunk allowed vlan 30 command on Fa0/5?It allows only VLAN 30 on Fa0/5.*It allows a native VLAN of 30 to be implemented on Fa0/5.It allows VLANs 1 to 30 on Fa0/5.It allows VLANs 10, 20, and 30 on Fa0/5.14Refer to the exhibit. A frame is traveling between PC-A and PC-B through the switch. Which statement is true concerning VLAN tagging of the frame?No VLAN tag is added to the frame.*A VLAN tag is added when the frame is accepted by the switch.A VLAN tag is added when the frame is forwarded out the port to PC-B.A VLAN tag is added when the frame leaves PC-A.15Refer to the exhibit. PC-A and PC-B are both in VLAN 60. PC-A is unable to communicate with PC-B. What is the problem?The native VLAN is being pruned from the link.The VLAN that is used by PC-A is not in the list of allowed VLANs on the trunk.*The trunk has been configured with the switchport nonegotiate command. The native VLAN should be VLAN 60.16What VLANs are allowed across a trunk when the range of allowed VLANs is set to the default value?All VLANs will be allowed across the trunk.*Only the native VLAN will be allowed across the trunk.The switches will negotiate via VTP which VLANs to allow across the trunk. Only VLAN 1 will be allowed across the trunk.17Under which two occasions should an administrator disable DTP while managing a local area network? (Choose two.)on links that should not be trunking*when connecting a Cisco switch to a non-Cisco switch*on links that should dynamically attempt trunkingwhen a neighbor switch uses a DTP mode of dynamic autowhen a neighbor switch uses a DTP mode of dynamic desirable18Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.Which PCs will receive the broadcast sent by PC-C?PC-D, PC-E*PC-A, PC-B, PC-D, PC-EPC-A, PC-BPC-A, PC-B, PC-D, PC-E, PC-FPC-A, PC-B, PC-E19Which two statements are true about VLAN implementation? (Choose two.)The network load increases significantly because of added trunking information.Devices in one VLAN do not hear the broadcasts from devices in another VLAN.*The size of the collision domain is reduced.VLANs logically group hosts, regardless of physical location.*The number of required switches in a network decreases.20Refer to the exhibit. DLS1 is connected to another switch, DLS2, via a trunk link. A host that is connected to DLS1 is not able to communicate to a host that is connected to DLS2, even though they are both in VLAN 99. Which command should be added to Fa0/1 on DLS1 to correct the problem?switchport trunk allowed vlan add 99switchport trunk native vlan 66*switchport mode dynamic autoswitchport nonegotiate21Which switch feature ensures that no unicast, multicast, or broadcast traffic is passed between ports that are configured with this feature?switch port securityPVLAN protected port*ACLVLAN22Fill in the blank. Use the full command syntax.The ” show vlan brief” command displays the VLAN assignment for all ports as well as the existing VLANs on the switch.23Which three statements accurately describe VLAN types? (Choose three).An 802.1Q trunk port, with a native VLAN assigned, supports both tagged and untagged traffic.*A management VLAN is any VLAN that is configured to access management features of the switch.*A data VLAN is used to carry VLAN management data and user-generated traffic.Voice VLANs are used to support user phone and e-mail traffic on a network. VLAN 1 is always used as the management VLAN.After the initial boot of an unconfigured switch, all ports are members of the default VLAN.*24Which command should the network administrator implement to prevent the transfer of DTP frames between a Cisco switch and a non-Cisco switch?S1(config-if)# switchport mode trunkS1(config-if)# switchport mode accessS1(config-if)# switchport nonegotiate*S1(config-if)# switchport mode dynamic desirableS1(config-if)# switchport trunk allowed vlan noneCCNA 2 - Chapter 41What type of IPv6 address is required as a minimum on IPv6 enabled interfaces?staticglobal unicastlink-local*loopbackunique local2In order for packets to be sent to a remote destination, what three pieces of information must be configured on a host? (Choose three.)default gateway*hostnameDNS server addressDHCP server addressIP address*subnet mask*3What two pieces of information are displayed in the output of the show ip interface brief command? (Choose two.)MAC addressesLayer 1 statuses*IP addresses*next-hop addressesinterface descriptionsspeed and duplex settings4Place the options in the following order:next hopdestination networkmetric- not scored -administrative distanceroute timestamproute source protocol- not scored -5Which two items are used by a host device when performing an ANDing operation to determine if a destination address is on the same local network? (Choose two.)destination MAC addressnetwork numberdestination IP address*source MAC addresssubnet mask*6Refer to the exhibit. A network administrator issues the show ipv6 route command on R1. What two conclusions can be drawn from the routing table? (Choose two.)Packets that are destined for the network 2001:DB8:ACAD:2::/64 will be forwarded through Fa0/1.R1 does not know a route to any remote networks.*The interface Fa0/1 is configured with IPv6 address2001:DB8:ACAD:A::12.*Packets that are destined for the network 2001:DB8:ACAD:2::54/128 will be forwarded through Fa0/0.The network FF00::/8 is installed through a static route command.7Refer to the exhibit. What is the purpose of the highlighted field in the line that is displayed from the show ip route command?It indicates that this is a directly connected route.It indicates that this route has been deleted from the routing table. It indicates that this route was learned via EIGRP.*It indicates that this is a default route.8Which two statements correctly describe the concepts of administrative distance and metric? (Choose two.)The metric varies depending which Layer 3 protocol is being routed, such as IP.A router first installs routes with higher administrative distances. The value of the administrative distance can not be altered by the network administrator.Routes with the smallest metric to a destination indicate the best path.* Administrative distance refers to the trustworthiness of a particular route.*The metric is always determined based on hop count.9What are two functions of a router? (Choose two.)It manages the VLAN database.It increases the size of the broadcast domain.It controls the flow of data via the use of Layer 2 addresses.It determines the best path to send packets.*It connects multiple IP networks.*10A packet moves from a host on one network to a device on a remote network within the same company. If NAT is not performed on the packet, which two items remain unchanged during the transfer of the packet from source to destination? (Choose two.)destination MAC addresssource ARP tablesource IP address*destination IP address*source MAC addressLayer 2 header11。
ccna第二学期练习答案
ERouting Chapter 1 - CCNA Exploration: 路由协议和概念 (版本1口令可用于限制对 Cisco IOS 所有或部分内容的访问。
请选择可以用口令保护的模式和接口。
（选择三项。
）VTY 接口控制台接口特权执行模式2路由器从相连的以太网接口收到消息后，会更改哪项报头地址，再将消息从另一个接口发送出去第 2 层源地址和目的地址3请参见图示。
网络管理员已经为路由器连接到直连网络的接口配置了如图所示的 IP 地址。
从路由器 ping 相连网络上的主机口之间相互 ping 都会遭到失败。
此问题最可能的原因是什么必须使用no shutdown命令启用接口。
4请参见图示。
主机 A ping 主机 B。
当 R4 收到对以太网接口的 ping 时，哪两块报头信息包括在内（选择两项。
）目的 IP 地址：目的 MAC 地址：5网络管理员刚把新配置输入 Router1。
要将配置更改保存到 NVRAM，应该执行哪一条命令Router1# copy running-config startup-config6您需要配置图中所示的串行连接，必须在 Sydney 路由器上发出以下哪条配置命令才能与 Melbourne 站点建立连接（选择三Sydney(config-if)# ip addressSydney no shutdownSydney(config-if)# clock rate 560007请参见图示。
从路由器的运行配置输出可得出什么结论显示的命令决定了路由器的当前运行情况。
8请参见图示。
在主机 2 连接到 LAN 上的交换机后，主机 2 无法与主机 1 通信。
导致此问题的原因是什么主机 1 和主机 2 位于不同的网络中。
9输入以下命令的作用是什么R1(config)# line vty 0 4R1(config-line)# password check123R1(config-line)# login设置通过 Telnet 连接该路由器时使用的口令10以下哪一项正确描述了路由器启动时的顺序加载 bootstrap、加载 IOS、应用配置11加载配置文件时的默认顺序是怎样的NVRAM、TFTP、CONSOLE12请参见图示。
CCNA考试自测题第3卷及答案
CCNA考试自测题第3卷及答案下面的问题将帮助你评价你在本章中学习到的内容。
仔细阅读所有的选项，因为正确答案可能多于1个。
选择每个问题中所有的正确答案。
1) The service provided by IPX is (IPX提供的服务是)：A. Guaranteed deliveryB. DatagramC. Connection-orientedD. Sequenced2) The Transport Control field in the IPX header holds what information? (IPX报头中的传输控制字段保留何种信息)？A. The age of the packet.B. Protocol typeC. Router hop countD. Level of service required.3) What is the length of an IPX network number (IPX网络编号的长度是多少)？A. 16 bitsB. VariableC. 48 bitsD. 32 bits4) In the IPX address 0102.0000.8045.1700, what is the node address ( 在I P X地址0 1 0 2 . 0 0 0 . 8 0 4 5 . 1 7 0 0中，节点地址是多少)？A. 1700B. 0102.0000.8045C. 0102.0000D. 0000.8045.1700A. It is the address of a NetWare print serverB. It is an internal network addressC. The included socket number is 0001D. Nothing6) The Checksum field in the IPX header is normally set to (IPX报头中的校验和字段通常设置为)：A. A checksum of the entire IPX packetB. A checksum of the IPX header fields onlyC. 0xFFFFD. 07) If an IPX node is configured to use the Ethernet_802.2 encapsulation, which other machines can it communicate with directly (without going through a router) on the same network (如果一个I P X节点配置为使用E t h e r n e t _ 8 0 2 . 3封装，它可以和相同网络上其他哪一个设备直接通信(不经过路由器) )？A. Machines running any encapsulationB. Machines running either Ethernet_802.2 or Ethernet_802.3C. Machines running Ethernet_IID. Machines running Ethernet_802.28) To run multiple encapsulations on a single physical interface, a router has to (为在一个物理接口上运行多个封装，路由器必须)：A. Use a different network number for each encapsulationB. Use subinterfaces, not secondary networksC. Enable NLSP routingD. Use an access list9) Which protocol does a workstation use to locate a server providing a particular type of service (工作站使用哪一个协议来找到提供特定类型服务的服务器)？B. NCPC. SAPD. EIGRP10) Periodic SAP updates are sent by (定期S A P更新由谁发出)：A. Routers and serversB. NetWare servers onlyC. Workstations and routersD. Workstations only11) The RIP protocol is used by (RIP协议由谁使用)？A. Routers onlyB. Servers onlyC. Workstations, servers, and routersD. Print servers12) Which command which must be given first to enable IPX (在启用I P X时，必须首先给出哪一个命令)？A. CISCO(CONFIG)#ENABLE IPX ROUTINGB. cisco>ipx routingC. cisco(config-if)#ipx routing onD. cisco(config)#ipx routing13) Which of the following allow you to use multiple IPX networks on a single physical interface (下面哪一个允许你在单个物理接口上使用多个I P X网络)？A. Secondary networksB. Dynamic frame typesC. Subinterfaces14) Which IOS command allows you to view the router’s internal SAP database (哪一个I O S 命令允许你查看路由器的内部S A P数据库)？A. SHOW SERV E R SB. show ipx serversC. serversD. ipx servers15) Which of the following kinds of information do you need to collect before you can configure IPX using IOS (你需要在用I O S配置I P X之前搜集下面各种信息中的哪一个)？A. The number of NetWare servers on the networkB. The encapsulations in useC. IPX network numbersD. The IPX address of another router16) What does this command do:CISCO(CONFIG-IF)#IPX NETWORK 3 (这个命令的作用是什么：C I S C O ( C O N F I G -IF)#IPX NETWORK3)：A. Nothing. It is incomplete.B. Sets up a static route to Network 3C. Configures IPX Network 3 on this interface with the default frame typeD. Nothing. The router is in the wrong configuration mode.17) What does this IOS command do?IPX ROUTE 4 5.0000.8004.4563 FLOAT I N G - S TATIC (这个I O S命令的作用是什么I P X ROUTE 45.0000.8004.4563 FLOAT I N G - S TAT I C )？A. Configures 4 static routesB. Configures static SAP entries for servers of type 4D. Says that to get to network 5, you must go via network 418) In the command IPX ROUTE 4 5.0000.8004.4563 FLOAT I N G - S TATIC, what does the F L O AT I N G - S TATIC keyword on the end mean? ( 在命令IPX ROUTE 45.0000.8004.4563F L O AT I N G.S TAT I C中，最后的F L O AT I N G.S TA T I C意味着什么)？A. Set all static routes to floatingB. Allow this route to be overridden by a route received dynamicallyC. Apply this route to all network numbers from 1 to 4D. Lock this route so that it cannot be changed19) The IPX MAXIMUM-PATHS command does what (IPX MAXIMUM.PAT H S命令的作用是什么)？A. Allows IOS to share traffic to a given network over multiple pathsB. Allows a slow link to be used as a backup for a faster oneC. Sets the maximum number of router hops a packet can travelD. Sets the maximum number of interfaces IPX can be configured on20) Which command is used to show a concise list of the configured IPX interfaces (哪一个命令用于显示配置的I P X接口上的简明列表)？A. SHOW CONFIGB. show ipx interfaceC. show ipx interface briefD. show interface21) If two devices are plugged into the same physical network, but are using diff e r e n t encapsulations, what it required before they can communicate (如果在相同的物理网络中加入了两个设备，但是使用不同的封装，在它们通信之前需要完成什么)？A. A cross-over cableB. A repeaterC. A router configured for the appropriate encapsulations22) When does a workstation normally send a GNS request (工作站一般在什么时候发出G N S请求)？A. When trying to communicate with another workstationB. When trying to locate the nearest routerC. When it needs to send a SAP updateD. When trying to locate a server at initialization23) How many router hops does a GNS request travel (一个G N S请求经过多少个路由器跳)？A. 16B. NoneC. 4D. Unlimited24) In a SAP update packet, what does the Server Address field contain (在S A P更新数据包中，服务器地址字段中包含什么)？A. The network the server is onB. The server’s node numberC. The socket number the server is listening onD. All of the above.25) Which of the following protocols is used by servers to advertise their services to the clients (下面协议中的哪一个由服务器使用，以向客户通告它们的服务)？A. Routing Information protocol (RIP)B. Sequenced Packet Exchange (SPX)C. Network Core Protocol (NCP)D. Service Advertising Protocol (SAP)26) On an Ethernet LAN how many IPX encapsulation types are supported (在一个E t h e r n e t局域网上，可以支持多少个I P X封装)？B. 3C. 2D. 127) The frame check sequence checks with which fields in an Ethernet_802.3 frame (帧校验序列校验E t h e r n e t - 8 0 2 . 3帧中的哪一个字段)？A. The Source Address and Destination AddresB. The packet dataC. Everything from the Destination Address onD. Source Service Access Point (SSAP)28) Which of the following fields is not common to both Ethernet_802.3 and Ethernet_802.2 frames (下面字段中的哪一个不是E t h e r e n e t 8 0 2 . 3和E t h e r n e t 8 0 2 . 3帧所共有的)？A. Source AddressB. LengthC. DSAPD. Data29) In SAP packets, the numbers in the Service Type field are assigned by (在一个S A P数据包中，服务类型字段中的数字由谁给定)？A. The system administratorB. The end userC. NovellD. Server30) SAP requests, responses, or broadcasts can be recognized by which value of source or destination socket number (SAP 请求，响应或广播可以通过源或目的套接字数字中的哪一个值来识别)？A. 0x0452C. 0x03D. 0x045331) In RIP Packets, the Hops Away and Time Ticks fields are valid both for request and response packets (在R I P数据包中，“跳距离”和“时间嘀嗒数”字段对于请求和响应数据包都是合法的)。
CCNA认证基础课程-课后作业.习题答案
CCNA认证基础-习题分析讲义第一部分第一章1. Convert the binary number 10111010 into its hexadecimal equivalent. Select thecorrect answer from the list below. （3）1) 852) 903) BA4) A15) B36) 1C2. Convert the Hexadecimal number A2 into its Base 10 equivalent. Select thecorrect answer from the list below. （4）1) 1562) 1583) 1604) 1625) 1646) 1663. Which binary number is a representation of the decimal number 248? （3）1) 111010002) 111101003) 111110004) 111110104. Which of the following will test the internal loopback of a node? （3）1) ping 10.10.10.12) ping 192.168.1.13) ping 127.0.0.14) ping 223.223.223.2235) ping 255.255.255.2555. What can be verified by successfully pinging the reserved loopback address ona host? （2）1) Connectivity exists between two hosts on the LAN.2) The TCP/IP stack of the local host is configured correctly.3) A connection exists between a host and the default gateway.4) The route a packet takes from the local host to a remote host is valid.6. Which of the following commands could be used on a Windows-basedcomputer to view the current IP configuration of the system? (Choose two.) （3，4）1) configip2) ifconfig3) ipconfig4) winipcfg5) Winipconfig7.Refer to the exhibit. What must be configured on Host B to allow it to communicate withthe Host C? (Choose three.) （2，4，6）1)the MAC address of RTA router interface connected to Switch 12) a unique host IP address3)the IP address of Switch 14)the default gateway address5)the MAC address of Host C6)the subnet mask for the LAN8. What are important characteristics to consider when purchasing a networkinterface card? (Choose two.) （2，3）1) security used on the network2) media used on the network3) system bus used on the computer4) software installed on the network5) diagnostic tools installed on the network第二章1. Select the necessary information that is required to compute the estimated timeit would take to transfer data from one location to another. (Choose two.) （1，5）1) file size2) data format3) network in use4) type of medium5) bandwidth of the link2. Using the data transfer calculation T=S/BW, how long would it take a 4MB file tobe sent over a 1.5Mbps connection? （2）1) 52.2 seconds2) 21.3 seconds3) 6.4 seconds4) 2 seconds5) 0.075 seconds6) 0.0375 seconds3. What are features of the TCP/IP Transport layer? (Choose two.) （3，5）1) path determination2) handles representation, encoding and dialog control3) uses TCP and UDP protocols4) packet switching5) reliability, flow control and error correction4. Which of the following is the Layer 4 PDU? （4）1) bit2) frame3) packet4) Segment5. What is important to remember about the data link layer of the OSI model whenconsidering Peer to Peer communication? (Choose three.) （3，4，5）1) It links data to the transport layer.2) It encapsulates frames into packets.3) It provides a service to the network layer.4) It encapsulates the network layer information into a frame.5) Its header contains a physical address which is required to complete the datalink functions.6) It encodes the data link frame into a pattern of 1s and 0s (bits) for transmissionon the medium.6. Which statement describes a star topology? （2）1) Each host in the network is connected to a backbone cable that is terminated atboth ends.2) Each host is connected to a hub or switch, either of which acts as a central pointfor all network connections.3) Each host is directly connected to two other hosts to form a long chain of hosts.4) Each host has a connection to all other hosts in the network.7. Which statements describe the logical token-passing topology? (Choose two.)（2）1) Network usage is on a first come, first serve basis.2) Computers are allowed to transmit data only when they possess a token.3) Data from a host is received by all other hosts. Electronic tokens are passedsequentially to each other.4) Token passing networks have problems with high collision rates.8. Which technologies are considered to be LAN technologies? (Choose two.) （2，5）1) DSL2) Token Ring3) Frame Relay4) ISDN5) Ethernet9.Refer to the exhibit. Host A wants to send a message to host B. Place the following stepsin the correct order so that the message can be sent. （4）A - add network layer addressesB - transmit bitsC - create application dataD - add data link layer addresses1) B, A, D, C2) D, A, C, B3) A, D, A, B4) C, A, D, B5) C, D, A, B6) C, B, A, D10.After an uns u ccessful ping to the local router, the technician decides to investigate therouter. The technician observes that the lights and fan on the router are not operational.In which layer of the OSI model is the problem most likely occurring? （4）1) transport2) network3) data link4) physical11. Refer t o the exhibit. What is the order of the TCP/IP Protocol Data Units as datais moved as indicated through the OSI model? （3）1) data, segments, frames, packets, bits2) data, packets, segments, frames, bits3) data, segments, packets, frames, bits4) data, packets, frames, segments, bits第三章1. Which combinations of charges will be repelled by electric force? (Choose two.)（4，6）1) neutral and neutral2) neutral and positive3) neutral and negative4) positive and positive5) positive and negative6) negative and negative2. Which of the following are considered the best media for use in data networkcommunications? (Choose three.) （2，3，6）1) glass2) fibers3) copper4) gold5) plastic6) silicon7) Silver3. Which of the following wireless standards increased transmission capabilitiesto 11 Mbps? （2）1) 802.11a2) 802.11b3) 802.11c4) 802.11d4. What is attenuation? （3）1) opposition to the flow of current2) measurement of electrical signals relative to time3) degradation of a signal as it travels along the medium4) amount or volume of traffic that is flowing on the medium5. Which cable specifications are indicated by 10BASE-T? （3）1) 10 Mbps transmission speed, baseband signal, 500 meter cable length, coaxialcable2) 10 Mbps transmission speed, broadband signal, 100 meter cable length, coaxialcable3) 10 Mbps transmission speed, baseband signal, 100 meter cable length,twisted-pair cable4) 10 Gbps transmission speed, broadband signal, 500 meter cable length,twisted-pair cable6. For which Ethernet installations would fiber optic rather than Cat5 UTP be abetter media choice? (Choose two.) （2，4）1) a 3 meter connection between two 10BASE-T hubs2) an environment with many potential sources of EMI and RFI3) a peer to peer connection between two NICs with RJ45 connectors4) an installation between two buildings that are located 500 meters apart5) a single building installation where installation costs are the major concern7. Refer to the exhibit. Which type of UTP cable should be used to connect Host Ato Switch1? （4）1) rollover2) console3) crossover4) straight-through8. Refer to the exhibit. Which type of Category 5 cable is used to make an Ethernetconnection between Host A and Host B? （3）1) coax cable2) rollover cable3) crossover cable4) straight-through cable第四章1. During cable testing, which of the following are used to calculate theinformation carrying capacity of a data cable? (Choose two.) （2，5）1) bit speed2) attenuation3) wire map4) saturation limit5) analog bandwidth2. What type of wiring problem is depicted in this sample of a cable tester? （3）1) a fault2) a short3) an open4) a split a good map3. In a new network installation, the network administrator has decided to use amedium that is not affected by electrical noise. Which cable type will best meet this standard? （5）1) coaxial2) screened twisted pair3) shielded twisted pair4) unshielded twisted pair5) fiber optic4. How does network cable length affect attenuation? （3）1) Category 5 cable that is run in metal conduit has the highest attenuation in theshortest distance.2) Shorter cable lengths have greater signal attenuation.3) Longer cable lengths have greater signal attenuation.4) The length of the cable has no effect on signal attenuation.第五章1. The highest capacity Ethernet technologies should be implemented in whichareas of a network? (Choose three.) （3，4，5）1) between workstation and backbone switch2) between individual workstations3) between backbone switches4) between enterprise server and switch5) on aggregate access links2. What device must be used between an AUI port of a networking device and themedia to which it is being connected? （3）1) a transducer2) a transmitter3) a transceiver4) a transponder5) a port replicator3. An ISDN Basic Rate Interface (BRI) is composed of how many signalingchannels? （1）1) 12) 23) 34) 44. Which layer of the OSI model covers physical media? （1）1) Layer 12) Layer 23) Layer 34) Layer 45) Layer 56) Layer 65. What type of network cable is used between a terminal and a console port? （3）1) cross-over2) straight-through3) rollover4) patch cable6. What is the recommended maximum number of workstations configured on apeer-to-peer network? （3）1) 252) 153) 104) 55) 27. Which of the following increases the potential for a collision to occur? （4）1) the use of an active hub instead of an intelligent hub2) the use of an intelligent hub instead of an active hub3) a reduction in the number of devices attached to the hub4) an increase in the number of devices attached to the hub8. What is the maximum length of a media segment used for 100BASE-TX? （1）1) 100 meters2) 185 meters3) 400 meters4) 500 meters9. Which cable diagram displays the end to end pinout for a crossover cable usedwith Cisco devices? （3）1) Cable A2) Cable B3) Cable C4) Cable D第六章1. What does the "10" in 10Base2 indicate about this version of Ethernet? （2）1) The version uses Base10 numbering within the frames.2) The version operates at a transmission rate of 10 Mbps.3) Frames can travel 10 meters unrepeated.4) The maximum frame length is 10 octets.2. How is a MAC address represented? （4）1) four groups of eight binary digits separated by a decimal point2) four Base10 digits separated by a decimal point3) six hexadecimal digits4) twelve hexadecimal digits5) twenty-four Base10 digits3. Which of the following statements are correct about CSMA/CD? (Choose three.)（1，3，6）1) It is a media access method used in LANs.2) It is a media access method used in FDDI WANs.3) When a device needs to transmit, it checks to see if the media is available.4) A device sends data without checking media availability because all deviceshave equal access.5) Multiple devices can successfully transmit simultaneously.6) Only one device can successfully transmit at a time.4. Which devices shown in the graphic must have a MAC address? （5）1) only PC2) only router3) PC and router4) PC, hub, and router5) PC, printer, and router第七章1. Which of the following items are common to all 100BASE technologies?(Choose three.) （1，4，5）1) frame format2) media3) connectors4) timing5) multi-part encoding2. Which of the following does 1000BASE-T use to accomplish gigabit speeds onCat 5e cable? （4）1) the use of four conductors in full-duplex mode2) the use of two multiplexed pairs of wires, simultaneously3) the use of three pairs of wires for data and the fourth for stabilization andforward error correction4) the use of all four pairs of wires in full-duplex mode, simultaneously3. For which of the following is Ethernet considered the standard? (Choose three.)（1，4，5）1) inter-building connection2) mid-length voice3) video conferencing4) vertical wiring5) horizontal wiring6) diagonal wiring4. To make sure timing limitations are not violated when implementing a 10 MbpsEthernet network involving hubs or repeaters, a technician should adhere to which rule? （4）1) the 4-5-3 rule2) the 6-4-2 rule3) the 3-4-5 rule4) the 5-4-3 rule5. What is the maximum distance that 10BASE-T will transmit data before signalattenuation affects the data delivery? （1）1) 100 meters2) 185 meters3) 300 meters4) 500 meters6. When using Category 5 UTP cable, which RJ-45 pin pairs are used to exchangedata between hosts on an Ethernet network? （2）1) 1 and 2; 4 and 52) 1 and 2; 3 and 63) 3 and 6; 7 and 84) 4 and 5; 7 and 8第八章1. John has been hired as the network administrator of a local company and hasdecided to add more hubs to the company's existing network. Which of the following has been caused by John's inexperience? （1）1) collision domain extended2) an increased number of collision domains3) increased network performance4) increased bandwidth5) extended bandwidth2. "CompA" is trying to locate a new computer named "CompB" on the network.Which of the following does "CompA" broadcast to find the MAC address of "CompB"? （2）1) MAC request2) ARP request3) ping4) Telnet5) proxy ARP3. Which of the following is a term associated with replacing hubs with switchesto increase the number of collision domains? （3）1) encapsulation2) latency3) segmentation4) layered model5) broadcast domain6) Extended4. The accumulation of traffic from which of the following can cause a networkcondition called broadcast radiation? (Choose three.) （3，5，6）1) anonymous FTP servers2) telnet sessions3) video over IP applications4) NAS services5) ARP requests6) RIP updates5. Which of the following describes the use of Spanning Tree Protocol (STP)? （4）1) resolve routing loops2) eliminate Split Horizon errors3) limit collisions4) resolve switching loops6. Which term describes the delay in time that occurs when a frame leaves itssource device and reaches its destination? （4）1) collision2) backoff3) attenuation4) latency5) broadcast7. Based on the graphic above, which of the following occurs as each host systemcomes on line in the topology? （2）1) The switch sends its MAC address to each host.2) The switch adds MAC address to the bridge table as each host sends a frame.3) Each host exchanges MAC addresses with each other.4) The switch listens for data traffic to block since the switch lacks an IP address. 8. Which devices segment collision domains? (Choose two.) （2，3）1) transceiver2) router3) switch4) hub5) media9. Which protocol is used to eliminate switching loops? （3）1) Transmission Control Protocol2) Routing Information Protocol3) Spanning Tree Protocol4) Interior Gateway Routing Protocol5) Internetworking Protocol10. Refer to the exhibit. A network associate needs to establish an Ethernetconnection between Host A and Host B. However, the distance between the two hosts is further than the cabling standards allow. Which two devices that operate at the physical layer of the OSI can be used to allow Host A and Host B to communicate? （2，5）1) switch2) hub3) bridge4) router5) repeater第九章1. Which term describes an ARP response by a router on behalf of a requestinghost? （3）1) ARP2) RARP3) Proxy ARP4) Proxy RARP2. Which protocol functions at the internet layer of the TCP/IP protocol suite? （4）1) File Transfer Protocol (FTP)2) Trivial File Transfer Protocol (TFTP)3) Transmission Control Protocol (TCP)4) Internet Protocol (IP)5) User Datagram Protocol (UDP)6) Simple Mail Transport Protocol (SMTP)3. Which of these workstation installation and setup tasks are concerned withnetwork access layer functions? (Choose two.) （2，4）1) configuring the e-mail client2) installing NIC drivers3) configuring IP network settings4) connecting the network cable5) using FTP to download application software updates4. Which part of an IP address identifies a specific device on a network? （4）1) first two octets2) third and fourth octets3) network portion4) host portion5) only the fourth octet5. Which of the following are features of the Internet Protocol (IP)? (Choose two.)（1，3）1) It is the most widely implemented global addressing scheme.2) It allows two hosts to share a single address on a local area network.3) It is a hierarchical addressing scheme allowing addresses to be grouped.4) It is only locally significant, used primarily on local area networks.6. Which of the following are useable Class A IP addresses with a default subnetmask? (Choose three.) （2，3，5）1) 127.0.39.12) 111.9.28.303) 123.1.2.1324) 128.50.38.25) 105.1.34.16) 0.23.92.37. Which application layer protocols use UDP at the transport layer? (Choose two.)（2，4）1) FTP2) SNMP3) Telnet4) DHCP5) SMTP第十章1. Which OSI layer encapsulates data into packets? （3）1) session2) transport3) network4) data link2. Which OSI layer defines the functions of a router? （3）1) physical2) data link3) network4) transport5) session3. Which of the following are Cisco proprietary routing protocols? (Choose two.)（2，6）1) RIPv22) IGRP3) OSPF4) BGP5) RIPv16) EIGRP4. A company with a Class B license needs to have a minimum of 1,000 subnetswith each subnet capable of accommodating 50 hosts. Which mask below is the appropriate one? （4）1) 255.255.0.02) 255.255.240.03) 255.255.255.04) 255.255.255.1925) 255.255.255.2245. A small company has a class C network license and needs to create five usablesubnets, each subnet capable of accommodating at least 20 hosts. Which of the following is the appropriate subnet mask? （3）1) 255.255.255.02) 255.255.255.1923) 255.255.255.2244) 255.255.255.2406. When a network administrator applies the subnet mask 255.255.255.248 to aClass A address, for any given subnet, how many IP addresses are available to be assigned to devices? （6）1) 10222) 5103) 2544) 1265) 306) 67. Host A is assigned the IP address 10.18.97.55 /21. How many more networkdevices can be assigned to this subnetwork if Host A is the only one that has an IP address assigned so far? （4）1) 2542) 5093) 10214) 20455) 40946) 81908.Refe r to the exhibit. The network administrator wants to create a subnet for thepoint-to-point connection between the two routers. Which subnetwork mask would provide enough addresses for the point-to-point link with the least number of wasted addresses?1) 255.255.255.1922) 255.255.255.2243) 255.255.255.2404) 255.255.255.2485) 255.255.255.2529. What is the correct number of usable subnetworks and hosts for the IP networkaddress 192.168.35.0 subnetted with a /28 mask?1) 6 networks / 64 hosts2) 14 networks / 32 hosts3) 14 networks / 14 hosts4) 30 networks / 64 hosts10. Which subnet masks would be valid for a subnetted Class B address? (Choosetwo.) （5，6）1) 255.0.0.02) 255.254.0.03) 255.224.0.04) 255.255.0.05) 255.255.252.06) 255.255.255.19211. Refer to the exhibit. How will the Fohi router dynamically learn routes to the192.168.16.16/28, 192.168.16.32/28, and 192.168.16.48/28 subnetworks? （3）1) with a static route2) with a routed protocol3) with a routing protocol4) with a directly connected route12. How many broadcast domains are shown in the diagram? （1）1) three2) four3) five4) six5) seven6) eight13. How many collision domains are shown in the diagram? （5）1) three2) four3) five4) six5) seven6) eight14. A router interface has been assigned an IP address of 172.16.192.166 with amask of 255.255.255.248. To which subnet does the IP address belong?1) 172.16.0.02) 172.16.192.03) 172.16.192.1284) 172.16.192.1605) 172.16.192.1686) 172.16.192.17615. Refer to the exhibit. Host A is sending data to Host B. Once R2 determines thatdata from Host A must be forwarded to R1 to reach Host B, which layer of the OSI model will R2 use to address and build the frames destined for R1?1) physical2) data link3) network4) transport5) session6) presentation16. Which type of address is 192.168.170.112/28?1) host address2) subnetwork address3) broadcast address4) multicast address17. Which type of address is 223.168.17.167/29?1) host address2) multicast address3) broadcast address4) subnetwork address18. Which combination of network id and subnet mask correctly identifies all IPaddresses from 172.16.128.0 through 172.16.159.255?1) 172.16.128.0 255.255.255.2242) 172.16.128.0 255.255.0.03) 172.16.128.0 255.255.192.04) 172.16.128.0 255.255.224.05) 172.16.128.0 255.255.255.19219. Refer to the exhibit. The internetwork in the exhibit has been assigned the IPaddress 172.20.0.0. What would be the appropriate subnet mask to maximize the number of networks available for future growth?1) 255.255.224.02) 255.255.240.03) 255.255.248.04) 255.255.252.05) 255.255.254.06) 255.255.255.0第十一章1. If a network administrator needed to download files from a remote server, whichprotocols could the administrator use to remotely access those files? (Choose two.) （3，5）1) NFS2) ASCII3) TFTP4) IMAP5) FTP6) UDP2. What is established during a connection-oriented file transfer betweencomputers? (Choose two.) （2，5）1) a temporary connection to establish authentication of hosts2) a connection used for ASCII or binary mode data transfer3) a connection used to provide the tunnel through which file headers aretransported4) a command connection which allows the transfer of multiple commands directlyto the remote server system5) a control connection between the client and server3. Which of the following protocols are used for e-mail transfer between clientsand servers? (Choose three.) （3，4，5）1) TFTP2) SNMP3) POP34) SMTP5) IMAP46) postoffice4. Which type of institution does the domain suffix .org represent? （4）1) government2) education3) network4) non-profit5. Which of the following services is used to translate a web address into an IPaddress? （1）1) DNS2) WINS3) DHCP4) Telnet6. Which part of the URL http://www.awsb.ca/teacher gives the name of thedomain? （4）1) www2) http://3) /teacher4) awsb.ca7. Which protocols are TCP/IP application layer protocols? (Choose two.) （2，4）1) UDP2) FTP3) IP4) SMTP5) TCP8. What are three characteristics of the TCP protocol? (Choose three.) （3，4，6）1) has less overhead than UDP2) is used for IP error messages3) forces the retransmission undelivered packets4) creates a virtual session between end-user applications5) carries the IP address of destination host in the TCP header6) is responsible for breaking messages into segments and reassembling9. Two peer hosts are exchanging data using TFTP. During the current session, adatagram fails to arrive at the destination. Which statement is true regarding the retransmission of the datagram? （2）1) Datagram retransmission requires user authentication.2) Datagram retransmission is controlled by the application.3) Datagram retransmission relies on the acknowledgements at transport layer.4) Datagram retransmission occurs when the retransmission timer expires in thesource host.案例学习1. 子网计算练习：Answer2. 子网号及广播地址计算练习Answer3. 子网规划练习：已知：给定一个C类地址201.16.5.0/24。
CCNA_ERouting_Chapter_3
1When multiple routing protocols have a route to the same destination network, what determines route is installed in the routing table?best metriclowest hop countgreatest available bandwidthlowest administrative distancelowest cost2A growing medium-sized manufacturing company recently began to have routing instability issue company uses static routes and has a mixture of over 30 Cisco and non-Cisco routers. The netw administrator has decided to convert the network to dynamic routing. What characteristics of pro should be considered in this selection process?Distance vector routing protocols, such as RIP, converge more quickly than do link-state rou protocols.EIGRP can be used on all of the routers in the company.OSPF can be used between the routers.An exterior routing protocol, such as BGP, is recommended for growing companies.3An engineer creates a static route by entering the Router(config)# ip route 10.0.0.0 255.255.25 192.168.1.2 command. What can be concluded about this route?The administrative distance of this route is 1.192.168.1.2 is the address of an interface on this router.This route will display as a directly connected network in the routing table.Packets with a destination IP address of 192.168.1.2 will be forwarded to the 10.0.0.0/24 ne 4W hat is the purpose of a routing protocol?It is used to build and maintain ARP tables.It provides a method for segmenting and reassembling data packets.It allows an administrator to devise an addressing scheme for the network.It allows a router to share information about known networks with other routers.It provides a procedure for encoding and decoding data into bits for packet forwarding.5Which two conditions would create a setting where the use of a distance-vector routing protocol efficient? (Choose two.)the network requires a special hierarchical designfast convergence of the network is crucialthe network is using a hub and spoke topologythe network is using a flat designthere are more than 15 hops between the most distant routers6Which command would the network administrator issue to determine if load balancing is in effect on a router?show ip protocolsshow ip routeshow ip interface briefshow ip interface7W hich of the following best describes the operation of distance vector routing protocols?They use hop count as their only metric.They only send out updates when a new network is added.They send their routing tables to directly connected neighbors.They flood the entire network with routing updates.8Which two statements correctly describe the concepts of administrative distance and metric? (Choose two.)Administrative distance refers to the trustworthiness of a particular route.A router first installs routes with higher administrative distances.The value of the administrative distance can not be altered by the network administrator.Routes with the smallest metric to a destination indicate the best path.The metric is always determined based on hop count.The metric varies depending which Layer 3 protocol is being routed, such as IP or IPX.9T he following line of code is present in the routing table:O 10.16.1.0/27 [110/129] via 192.168.1.5, 00:00:05, Serial0/0/1What does the number 129 indicate in this output?The cost for this link has a value of 129.The clock rate on this serial interface is set to 129,000.The next-hop router is 129 hops away from this router.This route has been updated 129 times in this routing table.10Which of the following conditions must be met in order for a network to have converged?The routers in the network are operating with dynamic routing protocols.The routers in the network are operating with compatible versions of IOS.The routers in the network are operating with the same routing tables.The routers in the network are operating with consistent routing knowledge.11Refer to the exhibit. Router1 and Router2 are running EIGRP. All interfaces are operational and packets can be forwarde networks. What information will be found in the routing table for Router1?Router1 will have 6 directly connected networks.The administrative distance of the route to network 172.16.0.0 will be 90.The metric for routes to 172.16.0.0 will be 1.The interface that is used to forward packets to 172.16.0.0 will always be the S0/1 interface.12W hich two statements are true regarding the advantages of the use of static routes? (Choose two).increased securityreduced effort in configuring routesthe administrator maintains control over routingeasier to implement in a growing networkreduces the chance of routing errorsincreased router resource usage13The following line of code is displayed in a routing table:R 209.165.201.0/24 [120/2] via 192.168.252.2, 00:00:16, S0/0/0What can be concluded from this output?A packet destined for host 192.168.252.2 will be forwarded out the interface connected to network 209.165.201.0/24The value, 120, is used to determine the best path when a router has more than one routing protocol configured for t destination network.This route was manually configured using the ip route command.192.168.252.2 is an interface on the router that produced this output.14W hat will be the result of the following commands?ORL(config)# interface fastethernet 0/0ORL(config-if)# ip address 172.16.3.1 255.255.255.0ORL(config-if)# no shutdownThe 172.16.3.0 network will be routed by any dynamic routing protocol automatically.A routing table entry is made to the 172.16.3.0 network with a code of "C".A static route is required to route traffic to the 172.16.3.0 network.The commands will be saved to the startup-configuration automatically.15Which two statements are true regarding classless routing protocols? (Choose two.)sends subnet mask information in routing updatessends complete routing table update to all neighborsis supported by RIP version 1allows for use of both 192.168.1.0/30 and 192.168.1.16/28 subnets in the same topologyreduces the amount of address space available in an organization16Which two statements are true regarding metrics? (Choose two.)RIP uses bandwidth as a metric.OSPF uses delay as a metric.EIGRP uses bandwidth as a metric.OSPF uses cost based on bandwidth as a metric.RIP uses delay as a metric.EIGRP uses hop count only as a metric.17W hy is fast convergence desirable in networks that use dynamic routing protocols?Routers will not allow packets to be forwarded until the network has converged.Hosts are unable to access their gateway until the network has converged.Routers may make incorrect forwarding decisions until the network has converged.Routers will not allow configuration changes to be made until the network has converged.18Refer to the exhibit. Which statement correctly describes how R1 will determine the best path to R2?R1 will install a RIP route using network A in its routing table because the administrative distance of RIP is higher thaR1 will install a RIP route using network A in its routing table because the path cost from RIP is lower than EIGRP.R1 will install an EIGRP route using network B in its routing table because the administrative distance of EIGRP is loR1 will install an EIGRP route using network B in its routing table because the path cost from EIGRP is lower than RR1 will install an EIGRP route and a RIP route in its routing table and load balance between them.19Refer to the exhibit. If RIP is the routing protocol, what is the value of the metric from router A to network 192.168.5.0/24?345662472420 A router learns two paths with equal metrics to a destination network via the RIP routing protocol. How will the router handlthe destination network?The router will install the first route it learned into the routing table.The router will install both routes in the routing table and load balance between the two.The router will put the first route in the routing table, and denote the second route as a backup route.The router will pick the path with the higher bandwidth and will place it in the routing table.。
CCNA2第3章答案
CCNA2第3章答案1. 第3章简介本章讨论了局域网的部署和故障排除。
局域网是一个小范围内的计算机网络，通常被用于连接办公室或住宅中的设备。
本章重点介绍了局域网的构建和故障排除的一些基本概念和技术。
2. 局域网构建局域网的构建需要考虑以下几个关键因素：2.1 路由器和交换机•路由器是一个网络设备，用于将数据包在不同网络之间转发。
它可以连接不同的局域网，并在它们之间进行通信。
路由器通常具有多个接口，每个接口都可以连接到一个局域网。
•交换机是一个网络设备，用于在局域网内转发数据帧。
它可以将数据帧从一个端口转发到另一个端口，以便设备可以进行通信。
交换机根据MAC地址来转发数据帧，这使得局域网中的设备可以直接通信，而不需要经过路由器。
2.2 VLAN•VLAN（Virtual Local Area Network）是一种将局域网分割为多个虚拟网络的技术。
每个VLAN都有自己的逻辑分组，并且设备只能与同一VLAN中的设备进行通信。
VLAN可以提高网络的性能和安全性。
•VLAN可以通过交换机进行配置。
管理员可以将不同的端口分配给不同的VLAN，从而实现不同设备之间的逻辑隔离。
2.3 IP地址规划•IP地址是互联网上的设备进行通信的唯一标识符。
在构建局域网时，我们需要使用IP地址来唯一标识每个计算机或设备。
•IP地址可以手动配置，也可以通过DHCP服务器进行自动分配。
3. 局域网故障排除在网络运行过程中，可能会出现一些故障。
在这种情况下，我们需要进行故障排除来找出问题所在，并采取相应的措施进行修复。
以下是一些常见的局域网故障排除步骤：3.1 确定问题范围首先，我们需要确定问题的范围。
问题可能只影响特定的设备或特定的网络部分。
通过确定问题的范围，我们可以更方便地定位故障的根源。
3.2 确认基本连接检查设备之间的物理连接是否正确。
确保电缆连接可靠，并且没有松动或损坏。
3.3 使用ping工具测试连接使用ping工具测试设备之间的连通性。
ccna第二学期练习答案中文
ERouting Chapter 1 - CCNA Exploration: 路由协议和概念(版本4.0)1口令可用于限制对Cisco IOS 所有或部分内容的访问。
请选择可以用口令保护的模式和接口。
（选择三项。
）VTY 接口控制台接口特权执行模式2路由器从相连的以太网接口收到消息后，会更改哪项报头地址，再将消息从另一个接口发送出去？第 2 层源地址和目的地址3请参见图示。
网络管理员已经为路由器连接到直连网络的接口配置了如图所示的IP 地址。
从路由器ping 相连网络上的主机口之间相互ping 都会遭到失败。
此问题最可能的原因是什么？必须使用no shutdown命令启用接口。
4请参见图示。
主机 A ping 主机B。
当R4 收到对以太网接口的ping 时，哪两块报头信息包括在内？（选择两项。
）目的IP 地址：192.168.10.134目的MAC 地址：9999.DADC.12345网络管理员刚把新配置输入Router1。
要将配置更改保存到NVRAM，应该执行哪一条命令？Router1# copy running-config startup-config6您需要配置图中所示的串行连接，必须在Sydney 路由器上发出以下哪条配置命令才能与Melbourne 站点建立连接？（选Sydney(config-if)# ip address 201.100.53.2 255.255.255.0Sydney(config-if)# no shutdownSydney(config-if)# clock rate 560007请参见图示。
从路由器的运行配置输出可得出什么结论？显示的命令决定了路由器的当前运行情况。
8请参见图示。
在主机 2 连接到LAN 上的交换机后，主机2 无法与主机 1 通信。
导致此问题的原因是什么？主机 1 和主机2 位于不同的网络中。
9输入以下命令的作用是什么？R1(config)# line vty 0 4R1(config-line)# password check123R1(config-line)# login设置通过Telnet 连接该路由器时使用的口令10以下哪一项正确描述了路由器启动时的顺序？加载bootstrap、加载IOS、应用配置11加载配置文件时的默认顺序是怎样的？NVRAM、TFTP、CONSOLE12请参见图示。
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1Which two statements correctly describe the concepts of administrative distanc metric? (Choose two.)Administrative distance refers to the trustworthiness of a particular route.A router first installs routes with higher administrative distances.The value of the administarive distance can not be altered by the networkRoutes with the smallest metric to a destination indicate the best path.The metric is always determined based on hop count.The metric varies depending which Layer 3 protocol is being routed, such as2Refer to the exhibit. Which statement correctly describes how R1 will determinepath to R2?R1 will install a RIP route using network A in its routing table because theadministrative distance of RIP is higher than EIGRP.R1 will install a RIP route using network A in its routing table because the pafrom RIP is lower than EIGRP.R1 will install an EIGRP route using network B in its routing table because th administrative distance of EIGRP is lower than RIP.R1 will install an EIGRP route using network B in its routing table because th cost from EIGRP is lower than RIP.R1 will install an EIGRP route and a RIP route in its routing table and load b between them.3 Which two statements are true regarding classless routing protocols? (Choosesends subnet mask information in routing updatessends complete routing table update to all neighborsis supported by RIP version 1allows for use of both 192.168.1.0/30 and 192.168.1.16/28 subnets in the sareduces the amount of address space available in an organization4 Which command would the network administrator issue to determine if load balin effect on a router?s how ip protocolss how ip routes how ip interface briefs how ip interface5 Which two conditions would create a setting where the use of a distance-vectorprotocol would be efficient? (Choose two.)the network requires a special hierarchical designfast convergence of the network is crucialthe network is using a hub and spoke topologythe network is using a flat designthere are more than 15 hops between the most distant routers6 What is the purpose of a routing protocol?It is used to build and maintain ARP tables.It provides a method for segmenting and reassembling data packets.It allows an administrator to devise an addressing scheme for the network.It allows a router to share information about known networks with other route It provides a procedure for encoding and decoding data into bits for packet forwarding.7 Which of the following best describes the operation of distance vector routing pThey use hop count as their only metric.They only send out updates when a new network is added.They send their routing tables to directly connected neighbors.They flood the entire network with routing updates.8 What attribute is associated with link-state routing protocols?split horizonpoison reverselow processor overheadshortest-path first calculations9 Why is fast convergence desirable in networks that use dynamic routing protocRouters will not allow packets to be forwarded until the network has converg Hosts are unable to access their gateway until the network has converged.Routers may make incorrect forwarding decisions until the network has conv Routers will not allow configuration changes to be made until the network ha converged.10 Which of the following conditions must be met in order for a network to have conThe routers in the network are operating with dynamic routing protocols.The routers in the network are operating with compatible versions of IOS.The routers in the network are operating with the same routing tables.The routers in the network are operating with consistent routing knowledge.11 Which two statements are true regarding metrics? (Choose two.)RIP uses bandwidth as a metric.OSPF uses delay as a metric.EIGRP uses bandwidth as a metric.OSPF uses cost based on bandwidth as a metric.RIP uses delay as a metric.EIGRP uses hop count only as a metric.12 Which two statements are true regarding the advantages of the use of static routes? (Choosincreased securityreduced effort in configuring routesthe administrator maintains control over routingeasier to implement in a growing networkreduces the chance of routing errorsincreased router resource usage13 The following line of code is displayed in a routing table:R 209.165.201.0/24 [120/2] via 192.168.252.2, 00:00:16, S0/0/0What can be concluded from this output?A packet destined for host 192.168.252.2 will be forwarded out the interface connected t209.165.201.0/24.The value, 120, is used to determine the best path when a router has more than one rou protocol configured for the same destination network.This route was manually configured using the ip route command.192.168.252.2 is an interface on the router that produced this output.14 What will be the result of the following commands?ORL(config)# interface fastethernet 0/0ORL(config-if)# ip address 172.16.3.1 255.255.255.0ORL(config-if)# no shutdownThe 172.16.3.0 network will be routed by any dynamic routing protocol automatically.A routing table entry is made to the 172.16.3.0 network with a code of "C".A static route is required to route traffic to the 172.16.3.0 network.The commands will be saved to the startup-configuration automatically.15 An engineer creates a static route by entering the Router(config)# ip route 10.0.0.0 255.255192.168.1.2 command. What can be concluded about this route?The administrative distance of this route is 1.192.168.1.2 is the address of an interface on this router.This route will display as a directly connected network in the routing table.Packets with a destination IP address of 192.168.1.2 will be forwarded to the 10.0.0.0/24 first.16Refer to the exhibit. Router1 and Router2 are running EIGRP. All interfaces are operational a packets can be forwarded between all networks. What information will be found in the routing Router1?Router1 will have 6 directly connected networks.The administrative distance of the route to network 172.16.0.0 will be 90.The metric for routes to 172.16.0.0 will be 1.The interface that is used to forward packets to 172.16.0.0 will always be the S0/1 interfa 17 The following line of code is present in the routing table:O 10.16.1.0/27 [110/129] via 192.168.1.5, 00:00:05, Serial0/0/1What does the number 129 indicate in this output?The cost for this link has a value of 129.The clock rate on this serial interface is set to 129,000.The next-hop router is 129 hops away from this router.This route has been updated 129 times in this routing table.18 A growing medium-sized manufacturing company recently began to have routing instability iscompany uses static routes and has a mixture of over 30 Cisco and non-Cisco routers. The n administrator has decided to convert the network to dynamic routing. What characteristics of should be considered in this selection process?Distance vector routing protocols, such as RIP, converge more quickly than do link-state protocols.EIGRP can be used on all of the routers in the company.OSPF can be used between the routers.An exterior routing protocol, such as BGP, is recommended for growing companies.19Refer to the exhibit. If RIP is the routing protocol, what is the value metric from router A to network 192.168.5.0/24?345662472420 A router learns two paths with equal metrics to a destination network via the RIP routing protwill the router handle packets to the destination network?The router will install the first route it learned into the routing table.The router will install both routes in the routing table and load balance between the two.The router will put the first route in the routing table, and denote the second route as a ba route.The router will pick the path with the higher bandwidth and will place it in the routing tabl。