ccna2答案第七章

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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。

CCNA2-Quiz-09

1.On a router running EIGRP, what database would maintain a list of feasible successors?routing tableneighbor tabletopology tableadjacency table2.Refer to the exhibit. This is the debug output from 2 directly connected EIGRP routers. They are not forming an adjacency. What is the cause?one router is a non-cisco routerthey have different autonomous-system numbersthey are using difference sequence numbersthey are sending incorrect hello types3.Refer to the exhibit. Which command will advertise the 192.168.1.64/30 network but notthe 192.168.1.32 network on router A?network 192.168.1.0network 192.168.1.0 255.255.255.0network 192.168.1.64 0.0.0.3network 192.168.1.64 0.0.0.7network 192.168.1.64 0.0.0.2554.What two actions will the EIGRP DUAL FSM take if a link to a network goes down? (Choose two.)put the route into passive modequery neighbors for a new routesearch routing table for a feasible successorrun the SPF algorithm to find a new successorsearch topology table for a feasible successor5.Refer to the exhibit. What is indicated by the P at the beginning of the topology entry?the route is in a stable statethe route is a preferred routeDUAL is searching for a better route to this destinationthe exit interface is in passive mode and EIGRP advertisements are blocked6.In which of the following tables does the EIGRP DUAL algorithm store the primary route to a destination? (Choose two.)routingtopologyneighborpathshortest path7.What information is maintained in the EIGRP topology database for a destination route? (Choose three.)the routing protocolthe feasible distance of the routethe highest cost of the routethe SRTT value for the routethe route cost as advertised by the neighboring routerthe physical address of the gateway interface8.Which of the following statements describes the bounded updates used by EIGRP?Bounded updates are sent to all routers within an autonomous system.Partial updates are sent only to routers that need the information.The updates are sent to all routers in the routing table.Updates are bounded by the routers in the topology table.9.Which of the following types of routes will be denoted by EX in EIGRP routing table entries? (Choose two.)routes learned from other routing protocolsroutes learned from any non-adjacent EIGRP routersany route with a hop count metric higher than 224EIGRP routes that originate in different autonomous systemsall passive routes in the routing table10.Host 192.168.1.66 in the network illustrated is unable to ping host 192.168.1.130. How must EIGRP be configured to enable connectivity between the two hosts? (Choose two.)R1(config-router)# network 192.168.1.128R1(config-router)# auto-summaryR1(config-router)# no auto-summaryR2(config-router)# no auto-summaryR2(config-router)# auto-summaryR2(config-router)# network 192.168.1.611.Which two statements describe characteristics of EIGRP? (Choose two.)EIGRP is a distance vector routing protocol.EIGRP supports classless routing and VLSM.EIGRP is classified as a link-state routing protocol.EIGRP uses TCP for reliable delivery of EIGRP update packets.With EIGRP, loop-free paths are achieved through the use of hold-down timers.EIGRP sends a periodic update every 30 minutes.12.Refer to the exhibit. Based on the output of show ip eigrp neighbors, what are two possible problems with adjacencies between Router1 and Router2? (Choose two.)The routers are configured with different EIGRP process IDs.Automatic summarization was disabled.The hello timer for R1 was altered.The serial interfaces for both routers are in different networks.No feasible successors were found.13.Refer to the exhibit. In the topology table, what do the numbers 3011840 and 3128695 represent?the route metric that is applied to those EIGRP routes for this routerthe trustworthiness of the routing information sourcethe composite of the hop count and bandwidth to that destination networkthe total metric for that network as advertised by the EIGRP neighbor14.Refer to the exhibit. EIGRP is the only routing protocol enabled on this network. No static routes are configured on this router. What can be concluded about network 198.18.1.0/24 from the exhibited output?A route to network 198.18.1.0/24 is not listed in the routing table.Packets that are destined for 198.18.1.0/24 will be forwarded to 198.18.10.6.EIGRP will perform equal cost load balancing across two paths when forwarding packets to 198.18.1.0/24.The router with interface 172.16.3.2 is a successor for network 198.18.1.0/24.15.Refer to the exhibit. All interfaces have been configured with the bandwidths that are shown in the exhibit. Assuming that all routers are using a default configuration of EIGRP as their routing protocol, what path will packets take from the 172.16.1.0/16 network to the 192.168.200.0/24 network?A,B,EA,C,EA,D,EPackets will load balance across the A,B,E and A,C,E paths.Packets will load balance across the A,B,E and A,D,E paths.Packets will load balance across the A,C,E and A,D,E paths.16.By default, which two metrics are used by EIGRP to determine the best path between networks?MTUloaddelaybandwidthreliability17.Which term defines a collection of networks under the administrative control of a single entity that presents a common routing policy to the Internet?autonomous systemcontiguous networksprocess IDBGP18.Refer to the exhibit. The company is using EIGRP with an autonomous system number of 10. Pings between hosts on networks that are connected to router A and those that are connected to router B are successful. However, users on the 192.168.3.0 network are unable to reach users on the 192.168.1.32 network. What is the most likely cause of this problem?IP classless is enabled and is causing the packet to drop.The command network 192.168.1.32 was not issued on router C.The routers are not configured in the same EIGRP routing domain.Automatic summarization of the networks is causing the subnetted routes to be dropped.19.In the command router eigrp 20, what is the purpose of the number 20?specifies the administrative distance for all EIGRP routesidentifies the autonomous system number this EIGRP process will advertisedetermines what metric is added to all advertised routesindicates the number of addresses in the EIGRP routing domain20.The show ip eigrp topology command output on a router displays a successor route and a feasible successor route to network 192.168.1.0/24. In order to reduce processor utilization, what does EIGRP do when the primary route to this network fails?The router sends query packets to all EIGRP neighbors for a better route to network 192.168.1.0/24.The DUAL FSM immediately recomputes the algorithm to calculate the next backup route.Packets that are destined for network 192.168.1.0/24 are sent out the default gateway instead.The backup route to network 192.168.1.0/24 is installed in the routing table.21.What administrative distance would a router assign to a default route in EIGRP that is learned from a source external to the autonomous system?15709017019022.Refer to the exhibit. Network 192.168.0.0/28 goes down. What type of packet does Router2 immediately send to Router1 and Router3?a query for network 192.168.0.0/28an acknowledgment packet to 224.0.0.9an update packet that is sent to 255.255.255.255a packet that contains the new routing table for R2unicast update packets to 192.168.1.1 and 192.168.2.1。

数字通信基础与应用(第二版)课后答案7章答案

这一个比特在接受时出现错误 7.11 下列效率为 1/2 的编码中哪些会引起灾难性错误传播？（a）g1(X) = X2, g2(X) = 1+ X + X3 （b）g1(X) = 1 + X2, g2(X) = 1 + X3 （c）g1(X) = 1 + X + X2, g2(X) = 1+ X + X3 + X4 （d）g1(X) = 1+ X + X3 + X4, g2(X) = 1+ X2 + X4 （e）g1(X) = 1+ X4 + X6 + X7, g2(X) = 1+ X3 + X4 （f）g1(X) = 1 + X3 + X4, g2(X) = 1+ X + X2 + X4
7.7 题 7.5.中的编码器会引起灾难性错误传播吗？举例证明你的结论。编码器会引起灾难性错误传播。从下列多项式可以看出:
g1 (x) 1 x2 (1 x)(1 x) g2 (x) x x2 x(1 x)
因为共同因子（1+x）的出现，编码器会引起灾难性错误传播。状态图分析如下
7.15 图 P7.5 描绘了约束长度为 2 的卷积码编码器（a）画出状态图、树状图和网格图。（b）假定来自编码器的接收信息序列为 1 1 0 0 1 0，采用前向长度为 2 的反馈译码算法译码该信息序列。
图 P7.5
(a)
00
a=0
01
11
b=1
10
0
a 1
00
00
a
11
00
a
01
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b

计算机网络自顶向下方法第七章中文版答案全文优选

WRI 研究生0601最新精选全文完整版（可编辑修改）7复习题流式存储音频/视频: 暂停/恢复, 重新定位, 快进, 实时交互的音频视频: 人们进行实时的通信和响应。

第一阵营：TCP/IP协议中的基本原理没有变化, 按照需求增加带宽, 仍然使用有超高速缓存, 内容分布, 多点覆盖的网络。

1.第二阵营: 提供一个可以使应用在网络中节省带宽的网络服务。

2.第三阵营: 有区别的服务: 提出了在网络边缘的简单分类和维护方案。

并且根据他们在路由队列中的级别给出了不同的数据包和级别。

6.1: 简单, 不需要meta file 和流媒体服务器3. 6.2：允许媒体播放器通过web服务器直接进行交互, 不需要流媒体服务器。

4. 6.3：媒体播放器直接与流媒体服务器进行交互, 以满足一些特殊的流媒体应用。

5.端到端时延是分组从源经过网络到目的地所需要的时间。

分组时延抖动是这个分组与下个分组的端到端时延的波动。

6.在预定的播放时间之后收到的分组不能被播放, 所以, 从应用的观点来看, 这个分组可以认为是丢失了。

7.第一种方案: 在每n个数据块之后发送一个冗余的数据块, 这个冗余的被。

【the redundant chunk is obtained byexclusive OR-ing the n original chunks】8.第二种方案：随起始的数据流发送一个低分辨率, 低比特率的方案, 这种交错不会增加数据流的带宽需求。

不同会话中的RTP流: 不同的多播地址同一会话中不同流: SSRC fieldRTP和RTCP分组通过端口号区别。

9.传达报告分组: 包括分组丢失部分的信息, 最后序列号, 两次到达时间间隔的抖动。

发送报告分组: 大部分目前产生的RTP分组的时间戳和wall clock time , 发送分组的数量, 发送字节的数量, 源描述分组: 发送方的e-mail 地址, 发送方的姓名, 产生RTP流的应用。

《计算机网络》第二版_部分习题参考答案

《计算机网络》第二版_部分习题参考答案第一章绪论1. 什么是计算机网络？什么是互联网？2. 计算机网络的最重要功能是什么？3. 按照网络覆盖范围的大小可以将网络划分哪几类？每一类各有什么特点？4. 无线网可以分为哪几种？每一种的特点是什么？5. 简述ISO/OSI参考模型中每一层的名称和功能。

6. 简述TCP/IP参考模型中每一层的名称和功能。

7. 比较ISO/OSI和TCP/IP参考模型的异同点。

第二章数据通信基础1．什么是数据、信号和传输？2．数字传输有什么优点？3．什么是异步传输方式？什么是同步传输方式？4．什么是单工、半双工和全双工传输方式？5．什么是信号的频谱与带宽？6．什么是信道的截止频率和带宽？7．简述信号带宽与数据率的关系。

8．有线电视公司通过CATV电缆为每个用户提供数字通信服务。

假设每个用户占用一路电视信号带宽（6MHz），使用64QAM技术，那么每个用户的速率是多少？答：根据香农定理C = 2*W*log2M由于采用64-QAM技术，所以其M为64，W为6MHz，代入香农定理计算得出C = 2*W*log2M = 2*6*5 = 60Mbps9．要在带宽为4kHz的信道上用4秒钟发送完20KB的数据块，按照香农公式，信道的信噪比应为多少分贝（取整数值）？答：（1）根据计算信道容量的香农定理C=W*log2(1+S/N)（2）按题意C=20K×8÷4＝40Kbps；而W＝4KHz（3）故得解：log2(1+ S/N)＝10；其中S/Pn=210-1=1023（4）dB=10log10(S/N)=10log10(1023)≈30，所以该信道的信噪比应为30分贝。

10．对于带宽为3kHz、信噪比为30dB的电话线路，如果采用二进制信号传输，该电话线路的最大数据率是多少？答：此题用香农定理来解答。

信道的带宽B=3000Hz，信/噪比S/N＝30dB，则10lg（S/N）= 30dB，∴S/N = 1000。

CCNA第一学期第7章章节考试题答案100%

1当设备从一个网络或子网移至另一个网络或子网时，下列哪两项陈述是正确的？（选择两项）必须重新分配第 2 层地址。

不应改变默认网关地址。

设备使用同一个第 2 层地址仍可正常工作。

需要将其它端口号分配给应用程序和服务。

必须重新分配第 3 层地址才能与新的网络通信。

2请参见图示。

假设图示中的网络已收敛，即路由表和ARP 表均完整，主机 A 将在发往www 以太网帧目的地址字段中放入以下哪个MAC 地址？00-1c-41-ab-c0-0000-0c-85-cf-65-c000-0c-85-cf-65-c100-12-3f-32-05-af3数据链路层帧尾有何主要作用？定义逻辑拓扑提供介质访问控制支持帧错误检测传送帧的路由信息4请参见图示。

PC 正在向笔记本电脑发送帧。

离开RouterB 时，帧中包括的源MAC 地址和源MAC - PC源MAC - RouterA 的S0/0源MAC - RouterB 的Fa0/1源IP - PC源IP - RouterA 的S0/0源IP - RouterB 的Fa0/15在网络中实现第2 层协议时应该考虑哪三个因素？（选择三项）所选的第 3 层协议网络的地址范围传输层定义的PDU物理层实现要连接的主机数量网络层编址？介质共享应用进程逻辑拓扑中间设备的功能7以太网帧中的前导码有何作用？作为数据的填充位用于同步计时用于标识源地址。

用于标识目的地址。

8请参见图示。

流量从PC 路由到笔记本电脑时，会进行多少次CRC 计算？12468169有关物理拓扑和逻辑拓扑的陈述，下列哪一项正确？逻辑拓扑始终与物理拓扑相同。

物理拓扑与网络传输帧的方法有关。

物理信号路径是按数据链路层协议定义的。

逻辑拓扑由节点之间的虚拟连接组成。

10网络管理员有责任以图形精确表示公司网络线路和设备在建筑内的位置。

这种图是什么？逻辑拓扑物理拓扑电缆路径线路网接入拓扑11请参见图示。

下列哪项陈述描述了图示网络使用的介质访问控制方法？三个网络全部采用CSMA/CA。

思科CCNA考试答案(全)

CCNA思科考试答案（全）第 1 章考试1一家拥有10 名员工的小型公司使用单个LAN 在计算机之间共享信息。

哪种类型连接适合此公司？由当地电话服务提供商提供的拨号连接能够使公司方便且安全地连接员工的虚拟专用网络通过当地服务提供商建立的私有专用线路通过当地服务提供商提供的宽带服务（如DSL）答案：4解析：对于这种小型办公室，比较适合通过被称为数字用户线路(DSL) 的常见宽带服务实现Internet 连接，这种服务由当地的电话服务提供商提供。

由于员工人数很少，带宽的问题并不突出。

如果公司较大，在远程站点有分支机构，则专用线路会更加适合。

如果公司员工需要通过Internet 与公司联系，则采用虚拟专用网。

2哪种网络情况需要使用WAN？员工工作站需要获取动态分配的IP 地址。

员工在出差时需要通过VPN 连接到公司电子邮件服务器。

分支机构的员工需要与同一园区网络上的另一座建筑物内的公司总部共享文件。

员工需要访问托管在其建筑物内DMZ 中的公司Web 服务器上的网页。

答案：2解析：当出差的员工需要通过WAN 连接到公司电子邮件服务器时，VPN 将通过WAN 连接在员工笔记本电脑与公司网络之间创建一个安全隧道。

通过DHCP 获取动态IP 地址是LAN 通信的功能。

在企业园区的不同建筑物之间共享文件可通过LAN 基础设施来实现。

DMZ 是企业LAN 基础设施内一个受保护的网络。

3以下哪项描述了WAN 的特征？WAN 和LAN 在同一地理范围内运行，但有串行链路。

WAN 网络归运营商所有。

所有串行链路均被视为WAN 连接。

WAN 可提供到园区主干网的终端用户网络连接。

答案：2解析：WAN 可用于将企业LAN 互连到远程分支机构站点LAN 和远程工作人员站点。

WAN 归运营商所有。

虽然WAN 连接一般通过串行接口实现，但并不是所有串行链路均连接至WAN。

LAN（而非WAN）可在组织中提供终端用户网络连接。

4电路交换WAN 技术的两个常见类型是什么？（请选择两项。

有机化学第二版-徐寿昌-课后答案

徐寿昌编《有机化学》第二版习题参考答案第二章烷烃1、用系统命名法命名下列化合物（1）2，3，3，4-四甲基戊烷（2）3-甲基-4-异丙基庚烷（3）3，3，-二甲基戊烷（4）2，6-二甲基-3，6-二乙基辛烷（5）2，5-二甲基庚烷（6）2-甲基-3-乙基己烷（7）2，2，4-三甲基戊烷（8）2-甲基-3-乙基庚烷2、试写出下列化合物的结构式(1) (CH3)3CC(CH2)2CH2CH3(2) (CH3)2CHCH(CH3)CH2CH2CH2CH3(3) (CH3)3CCH2CH(CH3)2(4) (CH3)2CHCH2C(CH3)(C2H5)CH2CH2CH3（5）(CH3)2CHCH(C2H5)CH2CH2CH3(6)CH3CH2CH(C2H5)2(7) (CH3)2CHCH(CH3)CH2CH3(8)CH3CH(CH3)CH2CH(C2H5)C(CH3)33、略4、下列各化合物的系统命名对吗？如有错，指出错在哪里？试正确命名之。

均有错，正确命名如下：（1）3-甲基戊烷（2）2，4-二甲基己烷（3）3-甲基十一烷（4）4-异丙基辛烷（5）4，4-二甲基辛烷（6）2，2，4-三甲基己烷5、（3）＞（2）＞（5）＞(1) ＞(4)6、略7、用纽曼投影式写出1，2-二溴乙烷最稳定及最不稳定的构象，并写出该构象的名称。

交叉式最稳定重叠式最不稳定8、构象异构（1），（3）构造异构（4），（5）等同）2），（6）9、分子量为72的烷烃是戊烷及其异构体(1) C(CH3)4(2) CH3CH2CH2CH2CH3 (3) CH3CH(CH3)CH2CH3(4) 同(1)10、分子量为86的烷烃是己烷及其异构体(1)(CH3)2CHCH(CH3)CH3(2) CH3CH2CH2CH2CH2CH3 , (CH3)3CCH2CH3(3)CH3CH2CH(CH3)CH2CH3(4)CH3CH2CH2CH(CH3)214、(4)＞（2）＞（3）＞(1)第三章烯烃1、略2、（1）CH 2=CH — （2）CH 3CH=CH — （3）CH 2=CHCH 2— CH 2CH CH 3MeH H i-PrEt Men-PrMe Me Et i-Prn-Pr (4)(5)(6)(7)3、（1）2-乙基-1-戊烯 (2) 反-3,4-二甲基-3-庚烯 (或(E)-3,4-二甲基-3-庚烯 (3) (E)-2,4-二甲基-3-氯-3-己烯 (4) (Z)-1-氟-2-氯-2-溴-1-碘乙烯(5) 反-5-甲基-2-庚烯或 (E)-5-甲基-2-庚烯 (6) 反-3,4-二甲基-5-乙基-3-庚烯 (7) (E) -3-甲基-4-异丙基-3-庚烯 (8) 反-3,4-二甲基-3-辛烯 4、略 5、略 6、CH 3CH 2CHCH 2CH 3CH 3CH 2CCHCH 3CH 3OH BrCH 3CH 2CCHCH 3CH 3Cl ClCH 3CH 2C CHCH 3CH 3OH OHCH 3CH 2CH CHCH 3CH 3OHCH 3CH 2COCH 3CH 3CHOCH 3CH 2CH CHCH 3CH 3Br(1)(2)(3)(4)(5)(6)(7)7、活性中间体分别为：CH 3CH 2+ CH 3CH +CH 3 (CH 3)3C + 稳定性: CH 3CH 2+ ＞ CH 3CH +CH 3 ＞ (CH 3)3C + 反应速度: 异丁烯＞丙烯＞乙烯8、略9、（1）CH 3CH 2CH=CH 2 (2)CH 3CH 2C(CH 3)=CHCH 3 (有顺、反两种) （3）CH 3CH=CHCH 2CH=C(CH 3)2 (有、反两种)用KMnO 4氧化的产物: (1) CH 3CH 2COOH+CO 2+H 2O (2)CH 3CH 2COCH 3+CH 3COOH (3) CH 3COOH+HOOCCH 2COOH+CH 3COCH 310、（1）HBr ，无过氧化物（2）HBr ，有过氧化物（3）①H 2SO 4 ，②H 2O （4）B 2H 6/NaOH-H 2O 2 （5）① Cl 2，500℃ ② Cl 2，AlCl 3（6）① NH 3，O 2 ② 聚合，引发剂（7）① Cl 2，500℃，② Cl 2，H 2O ③ NaOH 11、烯烃的结构式为：（CH 3）2C=CHCH 3 。

CCNA最全最实用的复习知识点

CCNA复习知识点第一章：网际互联1、什么是互联网络当用路由器将两个或多个LAN或WAN连接起来，并用协议（如IP）配置逻辑网络寻址方案时，就创建了一个互联网络。

2、网络分段随着网络规模的不断增长，LAN中的流量拥塞会变得让人无法忍受。

解决这个问题的方法是，将一个很大的网络划分为一些小的网络，称为网络分段。

可使用路由器、交换机、和网桥来实现网络分段。

3、广播域所谓广播域是指网段上所有设备的集合，这些设备收听到送往那个网段的所有广播。

4、在网络中使用路由器的好处A：默认时路由器不会转发广播B：路由器可以根据第3层（网络层）信息（比如IP地址）对网络进行过滤5、路由器的四种功能数据包转发数据包过滤网络之间的通信路径选择）模型Application Layer：是实际应用程序之间的接口。

还负责识别并建立想要通信的计算机一方的可用性，并决定想要的通信是否存在足够的资源。

Presentation Layer：为应用层提供数据，并负责数据转换和代码的格式化。

如数据压缩、加密解密、多媒体操作等。

Session Layer ：负责建立、管理和终止表示层实体之间的会话连接。

提供3种不同的方式来组织它们之间的通信，单工、半双工和全双工。

使不同应用程序的数据与其他应用程序的数据保持隔离。

-----------------------------上三层定义了终端系统中的应用程序将如何彼此通信------------------------------------------------下四层定义了怎样进行端到端的数据传输-----------------------------------Transport Layer ：将数据分段并重组为数据流。

在互联网络的发送方主机和目的主机之间建立逻辑连接。

提供的功能有：流量控制、可靠的（面向连接的、窗口机制、确认）或不可靠的通信。

Network Layer ：负责设备寻址，跟踪网络中设备的位置，并决定传送数据的最佳路径，这意味着网络层必须在位于不同地区的互联设备之间传送数据流。

ccna 章节与期末答案

第一章：正确答案：2.4.5•解析：由于不需要使用网络设备和专用服务器，对等网络易于创建，复杂性更低，且成本更少。

而且对等网络也没有集中管理。

这种网络安全性更低，不可扩展，而且那些同时充当客户端和服务器的设备可能性能更差正确答案：1解析：正确答案： 3.5解析：选择网络介质的条件包括：所选介质可以成功传送信号的距离、要安装所选介质的环境、必须传输的数据量和速度以及介质和安装的成本。

正确答案：3和4解析：终端设备上的应用程序可以生成数据，更改数据内容并且负责启动封装过程。

正确答案：1和4解析：终端设备会发出通过网络传输的数据。

中间设备会在链路发生故障时通过备用路径传输数据，并且会过滤数据传输以增强安全性。

网络介质提供网络消息的传输通道。

正确答案：4解析：外联网是公司外部的人或企业合作伙伴访问数据的网络区域。

内部网只描述通常仅供内部人员访问的网络区域。

当设备连接到有线网络时，有线LAN 会受BYOD（自带设备）影响。

使用大学无线LAN 的设备多为平板电脑和智能手机。

大学生主要使用无线WAN 来访问他们的手机运营商网络。

.正确答案：2解析：由于通过Internet 可以联系在线供应商，所以家庭用户通过Internet 进行网上购物。

内联网基本上是仅供内部使用的局域网。

外联网是外部合作伙伴访问组织内部特定资源的网络。

家庭用户并不一定使用LAN 来访问Internet。

例如，PC 可以通过调制解调器直接连接到ISP。

正确答案：1解析：内部网这个术语用于表示一个组织的私有局域网和广域网连接。

内部网的设计旨在仅允许该组织的成员、员工或其他获得授权的人员进行访问。

正确答案：2和4解析：电缆和DSL 均能实现高带宽、始终联网，并提供到主机计算机或LAN 的以太网连接。

10正确答案：2和3解析：移动电话连接需要使用移动电话网络。

卫星连接通常用于家庭或企业外部不便使用物理布线的位置。

11正确答案：2解析：当对网络资源的请求超出了可用容量时，网络就会变得拥堵。

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。

CCNA2《路由技术》的FINAL

Discovery的CCNA2 FINAL1、192.168.17.111/28 属于哪一类地址？C主机地址网络地址广播地址组播地址2 用户正尝试访问/ 但未成功。

必须在主机上设置哪两个配置值才能允许访问？（选择两项。

）ADDNS 服务器WINS 服务器HTTP 服务器默认网关Netbios3 有关在Cisco 路由器上使用debug ip rip 命令，下列哪两项描述是正确的？（选择两项。

）ADdebug ip rip 命令实时显示RIP 路由活动。

debug ip rip 命令可在用户执行配置模式下发出。

debug ip rip 命令显示了由show ip route 和show ip protocols 命令所显示的信息组合。

由于路由器的处理器使用率，debug ip rip 命令仅在必要时使用。

应尽可能地使用debug ip rip 命令来替代show ip route 命令。

4 TCP 怎样确保可靠地传输数据？B如果目的主机没有收到源主机发送的数据段，它会请求重新发送。

如果源主机未在预先确定的时间内收到确认信息，它将向目的主机重新发送数据。

TCP 使用三次握手的同步确认(SYN-ACK) 确保所有数据都已收到。

TCP 协议解释程序验证源主机和目的主机传输的数据。

5 某黑客尝试获取存储在公司网络内部某台服务器上的机密信息。

网络安全解决方案检测完整的数据包，确定这是一个威胁，所以阻止该数据包进入内部网络。

这一过程中哪项安全措施保护了网络？BIDSIPS基于主机的防火墙Anti-X 软件6 下列哪两个进程帮助路由器确定到达目的网络的路径？（选择两项。

）CD检测数据包中的源IP 地址来自相连路由器的ARP 请求手动配置路由来自其它路由器的更新DHCP 信息广播来自SMTP 管理信息库的更新7 客户向ISP 技术人员反映连通性问题。

技术人员就相关问题询问客户之后，发现除了FTP 外，所有网络应用程序都正常。

计算机网络自顶向下第七版第七章答案

计算机⽹络⾃顶向下第七版第七章答案Computer Networking: A Top-Down Approach,7th Edition计算机⽹络⾃顶向下第七版Solutions to Review Questions and ProblemsChapter 7 Review Questions1.In infrastructure mode of operation, each wireless host is connected to the largernetwork via a base station (access point). If not operating in infrastructure mode, a network operates in ad-hoc mode. In ad-hoc mode, wireless hosts have noinfrastructure with which to connect. In the absence of such infrastructure, the hosts themselves must provide for services such as routing, address assignment, DNS-like name translation, and more.2.a) Single hop, infrastructure-basedb) Single hop, infrastructure-lessc) Multi-hop, infrastructure-basedd) Multi-hop, infrastructure-less3.Path loss is due to the attenuation of the electromagnetic signal when it travelsthrough matter. Multipath propagation results in blurring of the received signal at the receiver and occurs when portions of the electromagnetic wave reflect off objects and ground, taking paths of different lengths between a sender and receiver. Interference from other sources occurs when the other source is also transmitting in the samefrequency range as the wireless network.4.a) Increasing the transmission powerb) Reducing the transmission rate5.APs transmit beacon frames. An AP’s beacon frames will be transmitted over one ofthe 11 channels. The beacon frames permit nearby wireless stations to discover and identify the AP.6.False7.APs transmit beacon frames. An AP’s beacon frames will be transmitted over one ofthe 11 channels. The beacon frames permit nearby wireless stations to discover and identify the AP.8.False9.Each wireless station can set an RTS threshold such that the RTS/CTS sequence isused only when the data frame to be transmitted is longer than the threshold. This ensures that RTS/CTS mechanism is used only for large frames.10.No, there wouldn’t be any advantage. Suppose there are two stations that want totransmit at the same time, and they both use RTS/CTS. If the RTS frame is as long asa DATA frames, the channel would be wasted for as long as it would have beenwasted for two colliding DATA frames. Thus, the RTS/CTS exchange is only useful when the RTS/CTS frames are significantly smaller than the DATA frames.11.Initially the switch has an entry in its forwarding table which associates the wirelessstation with the earlier AP. When the wireless station associates with the new AP, the new AP creates a frame with the wireless station’s MAC address and broadcasts the frame. The frame is received by the switch. This forces the switch to update itsforwarding table, so that frames destined to the wireless station are sent via the new AP.12.Any ordinary Bluetooth node can be a master node whereas access points in 802.11networks are special devices (normal wireless devices like laptops cannot be used as access points).13.False14.“Opportunistic Scheduling” refers to matching the physical layer protocol to channelconditions between the sender and the receiver, and choosing the receivers to which packets will be sent based on channel condition. This allows the base station to make best use of the wireless medium.15.UMTS to GSM and CDMA-2000 to IS-95.16.The data plane role of eNodeB is to forward datagram between UE (over the LTEradio access network) and the P-GW. Its control plane role is to handle registration and mobility signaling traffic on behalf of the UE.The mobility management entity (MME) performs connection and mobility management on behalf of the UEs resident in the cell it controls. It receives UE subscription information from the HHS.The Packet Data Network Gateway (P-GW) allocates IP addresses to the UEs and performs QoS enforcement. As a tunnel endpoint it also performs datagram encapsulation/decapsulation when forwarding a datagram to/from a UE.The Serving Gateway (S-GW) is the data-plane mobility anchor point as all UE traffic will pass through the S-GW. The S-GW also performs charging/billing functions and lawful traffic interception.17.In 3G architecture, there are separate network components and paths for voice anddata, i.e., voice goes through public telephone network, whereas data goes through public Internet. 4G architecture is a unified, all-IP network architecture, i.e., both voice and data are carried in IP datagrams to/from the wireless device to several gateways and then to the rest of the Internet.The 4G network architecture clearly separates data and control plane, which is different from the 3G architecture.The 4G architecture has an enhanced radio access network (E-UTRAN) that is different from 3G’s radio access network UTRAN.18.No. A node can remain connected to the same access point throughout its connectionto the Internet (hence, not be mobile). A mobile node is the one that changes its point of attachment into the network over time. Since the user is always accessing theInternet through the same access point, she is not mobile.19.A permanent address for a mobile node is its IP address when it is at its homenetwork. A care-of-address is the one its gets when it is visiting a foreign network.The COA is assigned by the foreign agent (which can be the edge router in theforeign network or the mobile node itself).20.False21.The home network in GSM maintains a database called the home location register(HLR), which contains the permanent cell phone number and subscriber profileinformation about each of its subscribers. The HLR also contains information about the current locations of these subscribers. The visited network maintains a database known as the visitor location register (VLR) that contains an entry for each mobile user that is currently in the portion of the network served by the VLR. VLR entries thus come and go as mobile users enter and leave the network.The edge router in home network in mobile IP is similar to the HLR in GSM and the edge router in foreign network is similar to the VLR in GSM.22.Anchor MSC is the MSC visited by the mobile when a call first begins; anchor MSCthus remains unchanged during the call. Throughout the call’s duration and regardless of the number of inter-MSC transfers performed by the mobile, the call is routed from the home MSC to the anchor MSC, and then from the anchor MSC to the visited MSC where the mobile is currently located.23.a) Local recoveryb) TCP sender awareness of wireless linksc) Split-connection approachesChapter 7 ProblemsProblem 1Output corresponding to bit d 1 = [-1,1,-1,1,-1,1,-1,1]Output corresponding to bit d 0 = [1,-1,1,-1,1,-1,1,-1]Problem 2Sender 2 output = [1,-1,1,1,1,-1,1,1]; [ 1,-1,1,1,1,-1,1,1]Problem 3181111)1()1(111111)1()1(1112=?+?+-?-+?+?+?+-?-+?=d 181111)1()1(111111)1()1(1122=?+?+-?-+?+?+?+-?-+?=dProblem 4Sender 1: (1, 1, 1, -1, 1, -1, -1, -1)Sender 2: (1, -1, 1, 1, 1, 1, 1, 1)Problem 5a) The two APs will typically have different SSIDs and MAC addresses. A wirelessstation arriving to the café will associate with one of the SSIDs (that is, one of the APs). After association, there is a virtual link between the new station and the AP. Label the APs AP1 and AP2. Suppose the new station associates with AP1. When the new station sends a frame, it will be addressed to AP1. Although AP2 will alsoreceive the frame, it will not process the frame because the frame is not addressed to it. Thus, the two ISPs can work in parallel over the same channel. However, the two ISPs will be sharing the same wireless bandwidth. If wireless stations in different ISPs transmit at the same time, there will be a collision. For 802.11b, the maximum aggregate transmission rate for the two ISPs is 11 Mbps.b) Now if two wireless stations in different ISPs (and hence different channels) transmitat the same time, there will not be a collision. Thus, the maximum aggregatetransmission rate for the two ISPs is 22 Mbps for 802.11b.Problem 6Suppose that wireless station H1 has 1000 long frames to transmit. (H1 may be an AP that is forwarding an MP3 to some other wireless station.) Suppose initially H1 is the onlystation that wants to transmit, but that while half-way through transmitting its first frame, H2 wants to transmit a frame. For simplicity, also suppose every station can hear every other station’s signal (that is, no hidden terminals). Before transmitting, H2 will sense that the channel is busy, and therefore choose a random backoff value.Now suppose that after sending its first frame, H1 returns to step 1; that is, it waits a short period of times (DIFS) and then starts to transmit the second frame. H1’s second frame will then be transmitted while H2 is stuck in backoff, waiting for an idle channel. Thus, H1 should get to transmit all of its 1000 frames before H2 has a chance to access the channel. On the other hand, if H1 goes to step 2 after transmitting a frame, then it too chooses a random backoff value, thereby giving a fair chance to H2. Thus, fairness was the rationale behind this design choice.Problem 7A frame without data is 32 bytes long. Assuming a transmission rate of 11 Mbps, the time to transmit a control frame (such as an RTS frame, a CTS frame, or an ACK frame) is (256 bits)/(11 Mbps) = 23 usec. The time required to transmit the data frame is (8256 bits)/(11 Mbps) = 751DIFS + RTS + SIFS + CTS + SIFS + FRAME + SIFS + ACK= DIFS + 3SIFS + (3*23 + 751) usec = DIFS + 3SIFS + 820 usecProblem 8a) 1 message/ 2 slotsb) 2 messages/slotc) 1 message/slota)i) 1 message/slotii) 2 messages/slotiii) 2 messages/slotb)i) 1 message/4 slotsii) slot 1: Message A→ B, message D→ Cslot 2: Ack B→ Aslot 3: Ack C→ D= 2 messages/ 3 slotsiii)slot 1: Message C→ Dslot 2: Ack D→C, message A→ BRepeatslot 3: Ack B→ A= 2 messages/3 slotsProblem 10a)10 Mbps if it only transmits to node A. This solution is not fair since only A is gettingserved. By “fair” it m eans that each of the four nodes should be allotted equal number of slots.b)For the fairness requirement such that each node receives an equal amount of dataduring each downstream sub-frame, let n1, n2, n3, and n4 respectively represent the number of slots that A, B, C and D get. Now,data transmitted to A in 1 slot = 10t Mbits(assuming the duration of each slot to be t)Hence,Total amount of data transmitted to A (in n1 slots) = 10t n1Similarly total amounts of data transmitted to B, C, and D equal to 5t n2, 2.5t n3, and t n4 respectively.Now, to fulfill the given fairness requirement, we have the following condition:10t n1 = 5t n2 = 2.5t n3 = t n4Hence,n2 = 2 n1n3 = 4 n1n4 = 10 n1Now, the total number of slots is N. Hence,n1+ n2+ n3+ n4 = Ni.e. n1+ 2 n1 + 4 n1 + 10 n1 = Ni.e. n1 = N/17Hence,n2 = 2N/17n3 = 4N/17n4 = 10N/17The average transmission rate is given by:(10t n1+5t n2+ 2.5t n3+t n4)/tN= (10N/17 + 5 * 2N/17 + 2.5 * 4N/17 + 1 * 10N/17)/N= 40/17 = 2.35 Mbpsc)Let node A receives twice as much data as nodes B, C, and D during the sub-frame.Hence,10tn1 = 2 * 5tn2 = 2 * 2.5tn3 = 2 * tn4i.e. n2 = n1n3 = 2n1n4 = 5n1Again,n1 + n2 + n3 + n4 = Ni.e. n 1+ n1 + 2n1 + 5n1 = Ni.e. n1 = N/9Now, average transmission rate is given by:(10t n1+5t n2+ 2.5t n3+t n4)/tN= 25/9 = 2.78 MbpsSimilarly, considering nodes B, C, or D receive twice as much data as any other nodes, different values for the average transmission rate can be calculated.Problem 11a)No. All the routers might not be able to route the datagram immediately. This isbecause the Distance Vector algorithm (as well as the inter-AS routing protocols like BGP) is decentralized and takes some time to terminate. So, during the time when the algorithm is still running as a result of advertisements from the new foreign network, some of the routers may not be able to route datagrams destined to the mobile node.b)Yes. This might happen when one of the nodes has just left a foreign network andjoined a new foreign network. In this situation, the routing entries from the oldforeign network might not have been completely withdrawn when the entries from the new network are being propagated.c)The time it takes for a router to learn a path to the mobile node depends on thenumber of hops between the router and the edge router of the foreign network for the node.Problem 12If the correspondent is mobile, then any datagrams destined to the correspondent would have to pass through the correspondent’s home agent. The foreign agent in the network being visited would also need to be involved, since it is this foreign agent thatnotifies the correspondent’s home agent of the location of the correspondent. Datagrams received by the correspondent’s home agent would need to be encapsulated/tunneled between the correspondent’s home agent and for eign agent, (as in the case of the encapsulated diagram at the top of Figure 6.23.Problem 13Because datagrams must be first forward to the home agent, and from there to the mobile, the delays will generally be longer than via direct routing. Note that it is possible, however, that the direct delay from the correspondent to the mobile (i.e., if the datagram is not routed through the home agent) could actually be smaller than the sum of the delay from thecorrespondent to the home agent and from there to the mobile. It would depend on the delays on these various path segments. Note that indirect routing also adds a home agent processing (e.g., encapsulation) delay.Problem 14First, we note that chaining was discussed at the end of section 6.5. In the case of chaining using indirect routing through a home agent, the following events would happen: ?The mobile node arrives at A, A notifies the home agent that the mobile is now visiting A and that datagrams to the mobile should now be forwarded to thespecified care-of-address (COA) in A.The mobile node moves to B. The foreign agent at B must notify the foreign agent at A that the mobile is no longer resident in A but in fact is resident in Band has the specified COA in B. From then on, the foreign agent in A willforward datagrams it receives that are addressed to the mobile’s COA in A to t he mobile’s COA in B.The mobile node moves to C. The foreign agent at C must notify the foreign agent at B that the mobile is no longer resident in B but in fact is resident in C and has the specified COA in C. From then on, the foreign agent in B will forwarddatagrams it receives (from the foreign agent in A) that are addressed to themobile’s COA in B to the mobile’s COA in C.Note that when the mobile goes offline (i.e., has no address) or returns to its home network, the datagram-forwarding state maintained by the foreign agents in A, B and C must be removed. This teardown must also be done through signaling messages. Note that the home agent is not aware of the mobile’s mobility beyond A, and that the correspondent is not at all aware of the mobil e’s mobility.In the case that chaining is not used, the following events would happen: ?The mobile node arrives at A, A notifies the home agent that the mobile is now visiting A and that datagrams to the mobile should now be forwarded to thespecified care-of-address (COA) in A.The mobile node moves to B. The foreign agent at B must notify the foreign agent at A and the home agent that the mobile is no longer resident in A but infact is resident in B and has the specified COA in B. The foreign agent in A can remove its state about the mobile, since it is no longer in A. From then on, thehome agent will forward datagrams it receives that are addressed to the mobile’sCOA in B.The mobile node moves to C. The foreign agent at C must notify the foreign agent at B and the home agent that the mobile is no longer resident in B but in fact is resident in C and has the specified COA in C. The foreign agent in B canremove its state about the mobile, since it is no longer in B. From then on, thehome agent will forward datagrams it receives that are addressed to the mobile’sCOA in C.When the mobile goes offline or returns to its home network, the datagram-forwarding state maintained by the foreign agent in C must be removed. This teardown must also bedone through signaling messages. Note that the home agent is always aware of the mobile’s cu rrent foreign network. However, the correspondent is still blissfully unaware of the mobile’s mobility.Problem 15Two mobiles could certainly have the same care-of-address in the same visited network. Indeed, if the care-of-address is the address of the foreign agent, then this address would be the same. Once the foreign agent decapsulates the tunneled datagram and determines the address of the mobile, then separate addresses would need to be used to send the datagrams separately to their different destinations (mobiles) within the visited network.Problem 16If the MSRN is provided to the HLR, then the value of the MSRN must be updated in the HLR whenever the MSRN changes (e.g., when there is a handoff that requires the MSRN to change). The advantage of having the MSRN in the HLR is that the value can be provided quickly, without querying the VLR. By providing the address of the VLR Rather than the MSRN), there is no need to be refreshing the MSRN in the HLR.。

思科章节练习第二章到第七章试题及答案

思科章节练习第二章到第七章试题及答案第二章1.下列哪些陈述正确指出了中间设备在网络中的作用？（选择三项） (135) 确定数据传输路径发起数据通信重新定时和重新传输数据信号发送数据流管理数据流数据流最后的终止点2.请选择关于网络协议的正确陈述。

（选择三项。

135）定义特定层 PDU 的结构规定实现协议层功能的方式概述层与层之间通信所需的功能限制了对硬件兼容性的需要需要取决于协议层的封装过程杜绝厂商之间的标准化3.封装的两个功能是什么？（45选择两项）跟踪终端设备之间的延迟为通信提供统一的网络路径在传输前可以修改原始数据标识属于同一通信的数据片段确保数据片段可以转发到正确的接收端设备4.数据链路层封装添加的报尾信息有何主要功能？1支持差错校验确保数据按照顺序到达确保送达正确目的标识本地网络中的设备帮助中间设备进行处理和路径选择5.OSI 模型哪两层的功能与 TCP/IP 模型的网络接入层相同？（选择两项34）网络层传输层物理层数据链路层会话层6.什么是 PDU？4传输期间的帧损坏在目的设备上重组的数据因通信丢失而重新传输的数据包特定层的封装7.以下哪种特征正确代表了网络中的终端设备？ 2管理数据流发送数据流重新定时和重新传输数据信号确定数据传输路径8.IP 地址为 10.0.0.34 的“手机A”已经与 IP 地址为 172.16.1.103 的“IP 电话1”建立了 IP 会话。

请根据图示回答，下列哪个设备类型是对无线设备“手机A”功能的最准确描述？ 2目的设备终端设备中间设备介质设备9.下列哪三个标签正确标识了图示网段的网络类型？（236选择三项）网络 A -- WAN网络 B -- WAN网络 C -- LAN网络 B -- MAN网络 C -- WAN网络 A -- LAN10.下列哪三项陈述是对局域网 (LAN) 最准确的描述？（选择三项125）LAN 通常位于一个地域内。

此类网络由由一个组织管理。

计算机网络课后题答案第七章课后习题答案

第七章网络安全7-01 计算机网络都面临哪几种威胁？主动攻击和被动攻击的区别是什么？对于计算机网络的安全措施都有哪些？答：计算机网络面临以下的四种威胁：截获（interception），中断(interruption)，篡改(modification),伪造（fabrication）。

网络安全的威胁可以分为两大类：即被动攻击和主动攻击。

主动攻击是指攻击者对某个连接中通过的PDU 进行各种处理。

如有选择地更改、删除、延迟这些PDU。

甚至还可将合成的或伪造的PDU 送入到一个连接中去。

主动攻击又可进一步划分为三种，即更改报文流；拒绝报文服务；伪造连接初始化。

被动攻击是指观察和分析某一个协议数据单元PDU 而不干扰信息流。

即使这些数据对攻击者来说是不易理解的，它也可通过观察PDU 的协议控制信息部分，了解正在通信的协议实体的地址和身份，研究PDU 的长度和传输的频度，以便了解所交换的数据的性质。

这种被动攻击又称为通信量分析。

还有一种特殊的主动攻击就是恶意程序的攻击。

恶意程序种类繁多，对网络安全威胁较大的主要有以下几种：计算机病毒；计算机蠕虫；特洛伊木马；逻辑炸弹。

对付被动攻击可采用各种数据加密动技术，而对付主动攻击，则需加密技术与适当的鉴别技术结合。

7-02 试解释以下名词：（1）重放攻击；（2）拒绝服务；（3）访问控制；（4）流量分析；（5）恶意程序。

答：（1）重放攻击：所谓重放攻击（replay attack）就是攻击者发送一个目的主机已接收过的包，来达到欺骗系统的目的，主要用于身份认证过程。

（2）拒绝服务：DoS(Denial of Service)指攻击者向因特网上的服务器不停地发送大量分组，使因特网或服务器无法提供正常服务。

（3）访问控制：（access control）也叫做存取控制或接入控制。

必须对接入网络的权限加以控制，并规定每个用户的接入权限。

（4）流量分析：通过观察PDU 的协议控制信息部分，了解正在通信的协议实体的地址和身份，研究PDU 的长度和传输的频度，以便了解所交换的数据的某种性质。

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第七章 CCNA第二学期 Exploration: 路由协议和概念 (版本 4.0)(2010-12-20 19:19:52)转载▼标签：it 分类：2010｜CCNA2官方试题--路由ERouting Chapter 7 - CCNA Exploration: 路由协议和概念(版本 4.0)1请参见图示。

如果所有路由器都运行 RIP 第 2 版，为什么没有 192.168.1.32/27网络的路由Rip 第 2 版不会在更新中发送子网掩码。

路由器 A 并未将 RIP 设置为路由协议。

Rip 第 2 版默认将自动总结路由。

路由器 B 未设置为通告 192.168.1.64/30 网络。

2请参见图示。

下列哪个路由器上的哪条命令可让 Router1 获知 192.168.0.0/20 网络？Router1(config)# ip classlessRouter1(config-router)# no passive-interface serial 0/1/1Router2(config-router)# version 2Router2(config-router)# neighbor 10.0.0.23哪两项是选择实施 RIP 第 2 版而不是 RIP 第 1 版的原因？（选择两项。

）RIP 第 2 版支持 VLSM。

RIP 第 2 版支持 16 台以上的路由器。

RIP 第 2 版支持有类（而不是无类）路由RIP 第 2 版支持路由更新验证。

RIP 第 2 版支持多区域。

RIP 第 2 版使用 Dijkstra 算法而不是贝尔曼-福特算法。

4RIP v1 和 RIP v2 的相似点有哪些？（选择三项。

）两者都使用跳数作为度量。

两者对无穷距离使用相同的度量值。

两者都向邻居广播其更新。

两者都在更新中发送子网掩码信息。

两者都对更新来源进行身份验证。

两者都使用水平分割来防止路由环路。

5请参见图示。

路由器 East 和 West 被配置为使用 RIPv1。

两台路由器都会发送有关其直连路East 路由器可以 ping 通 West 路由器的串行接口，West 可以 ping 通 East 的串行接口。

台路由器都无法从对方动态获知路由。

最可能的原因是什么？需要配置最后选用网关。

子网划分不受 RIPv1 支持。

VLSM 不受 RIPv1 支持。

其中一台路由器的串行接口需要时钟频率。

6请参见图示。

下列哪条命令可让 Router2 获知 192.168.16.0/28 网络？Router1(config)# ip classlessRouter1(config-router)# network 192.168.16.0Router1(config-router)# no passive-interface serial 0/1/1Router2(config-router)# version 2Router2(config-router)# neighbor 10.0.0.27请参见图示。

所有路由器都运行 RIP 第 2 版。

JAX 被配置为仅通告 10.0.0.0/24 网络。

CHI 通告 172.16.0.0/16 网络。

网络管理员输入如图所示的命令。

该网络中将会发生什么变化？由于水平分割的原因，JAX 路由器将忽略 172.16.0.0/16 网络的更新。

CHI 将在其路由表中安装到 192.168.0.0/16 网络的路由。

CHI 的路由表中将包含 192.168.0.0/16 路由，但该路由旁边将标记 S。

ORL 路由器将对其路由更新中转发的所有网络应用 255.255.0.0 子网掩码。

8请参见图示。

技术人员需要添加一个新的环回接口以便测试路由运作情况和网络设计。

该技术由器上输入下列一组命令：Sanford(config)# interface loopback1Sanford(config-if)# ip address 192.168.6.62 255.255.255.252为什么该路由器返回错误？该路由器不允许环回接口配置。

该掩码不能用于这个地址类。

在添加这个地址之前必须配置无类路由。

Loopback1 的网络地址与之前配置的接口地址重叠。

该路由器已经超出其路由表所能提供的最大路径数限制。

9RIPv2 的默认度量允许的最大网络直径为多少？15 跳16 跳100 跳120 跳255 跳10配置路由协议时使用network命令有哪两项作用？（选择两项。

）标识将包含在路由更新中的网络标识网络中可以进行总结的主机地址用于列出远程和本地网络的所有地址确定要对路由更新应用的子网掩码确定哪些接口可以发送和接收路由更新11请参见图示。

从如图所示的输出中能得到什么结论？路由表被限制为只能有 2 条路由。

LAN 接口参与了路由过程。

已经从每个串行接口各发出一个更新并已收到 2 个更新。

此路由器上未配置no auto-summary。

12网络管理员被告知公司的 IP 地址基础架构必须符合 RFC 1918。

管理员可以在该网络中使用规定的哪三个 IP 地址范围？（选择三项。

）10.0.0.0/8127.0.0.0/8169.254.0.0/16172.16.0.0/12192.168.0.0/16209.165.201.0/2713请参见图示。

所有路由器都运行 RIPv1。

如果在路由器 B 上配置了地址为 10.16.1.129/27 的那么路由器 B 的路由表将发生什么变化？将添加到 10.16.1.0/27、10.16.1.64/27 和 10.16.1.128/27 网络的路由。

将添加到 10.16.1.128/27 网络的相连路由。

将添加来源为 RIPv1 的第三条到 10.0.0.0/8 网络的路由。

配置路由器 B 之后，路由表将立即删除 10.0.0.0/8 路由。

14网络管理员安装了四台运行 RIPv2 的新路由器。

Router1 是 RIPv2 网络中的边界路由器，其默认路由。

当网络收敛后，网络管理员在 Router1 上输入 Router1(config-router)# default-information originate。

该命令将对网络产生什么影响？阻止 Router1 转发有关非直连网络的更新使网络中的所有路由器都与 Router1 同步路由更新强制 Router1 成为更新的主要路由器或指定路由器 (DR)向网络中的所有路由器传播默认路由15请参见图示。

如图所示的网络中同时包含 Cisco 路由器和非 Cisco 路由器。

JAX 路由器上输debug ip rip。

目前所有路由器都运行相同版本的 RIP。

路由器 CHI 和路由器 ORL 无法到达192.168.1.16/28 网络。

使用什么方法可能解决此问题？在网络中启用水平分割。

在路由器上配置 RIPv2。

在 JAX 路由器的 RIP 配置中添加网络 192.168.1.0。

将 JAX Fa0/0 配置为被动接口。

启用 JAX 路由器上的 Serial0/0/0 接口。

将 JAX 路由器 Fa0/0 接口的 IP 地址更改为 192.168.1.1/24。

16为了支持 VLSM 和 CIDR，RFC 1723 在 RIP 消息报头中添加了什么字段？子网掩码目的端口号地址族标识符源和目的 IP 地址17请参见图示。

如图所示的命令对 Router1 的 RIP 更新会产生什么影响？只有第 2 版更新会发送到 255.255.255.255。

只有第 2 版更新会发送到 224.0.0.9。

第 1 版和第 2 版更新都会发送到 224.0.0.9。

第 1 版和第 2 版更新都会发送到 255.255.255.255。

18请参见图示。

RIPv1 是如图所示网络的路由协议。

在每台路由器上使用以下命令：router ripnetwork 10.0.0.0network 172.16.0.0完成上述配置后，每台路由器的 LAN 上的用户都无法访问远程 LAN。

为什么？network 语句配置错误。

形成了路由环路。

RIPv1 无法路由至主网的不连续子网。

RIPv1 无法路由使用 /24 子网掩码的网络。

19网络中的路由器使用 RIPv2 作为路由协议。

已经在路由器上输入了命令 Router(config-rout version 2。

输入该命令对路由更新会产生什么影响？子网掩码将添加到路由更新中。

路由更新将通过组播地址 224.0.0.9 发送出去。

将接收第 1 版和第 2 版更新，但不会发送第 2 版更新。

RIP 路由过程将从路由器上删除，不会再转发路由更新。

（注：本资料素材和资料部分来自网络，仅供参考。

请预览后才下载，期待你的好评与关注！）。

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