cisco期末复习题(含答案)(一)培训资料
思科第一学期期末练习题
1请参见图示。
哪种逻辑拓扑是对图示网络的准确描述？星型环型点对点多路访问2请参见图示。
电缆 1 和电缆2 的两端分别按照特定的物理层要求接线。
表中按编号列出了每个网段以及网络技术人员在该网段不同网络组件之间已经安装的电缆。
根据给定的数据回答，哪些网段的电缆安装正确？（选择三项）网段 1网段 2网段 3网段 4网段 53在封装过程中，传输层添加什么标识符？源IP 地址和目的IP 地址源端口号和目的端口号源通道标识符和目的通道标识符4下列哪三项是CSMA/CD 的特征？（选择三项。
）监测介质中是否存在数据信号。
检测到冲突后，主机可以在随机延迟时间到期后尝试重新传输。
使用堵塞信号以确保网络中的所有主机都获悉已发生冲突。
可以将设备配置为较高的传输优先级。
仅当存在数据信号时，才传输数据。
使用令牌系统来避免冲突。
5网络管理员想要限制访问路由器的特权执行模式。
管理员应该使用哪一种口令？使能aux控制台VTY6在Cisco IOS 设备中，启动配置文件存储于何处？闪存NVRAMRAMROM7由于发生安全规规事件，必须更改路由器口令。
从以下配置项可获知什么信息？（选择两项）Router(config)# line vty 0 4Router(config-line)# password arj15Router(config-line)# login此配置允许用户使用调制解调器建立连接。
用户在建立连接时必须指定要连接到线路0 还是线路4。
此配置允许用户使用telnet命令连接到路由器。
此配置同一时间允许五名用户与此路由器建立连接。
该路由器上自动加密配置的口令。
8请参见图示。
下列有关计算机 A 与服务器之间电子邮件传输的说法中哪一项正确？服务器将使用HTTP 将邮件传送到计算机A。
计算机 A 将连接到服务器并使用POP 检索入站邮件。
计算机 A 上的电子邮件客户端使用SMTP 从服务器收取入站邮件并将出站邮件传送到服务器。
思科第一学期期末考试最新考题CCNA1
1Refer to the exhibit. Which Layer 2 protocol could be used inside nework A and network C?IPTCPUDPEthernet2Refer to the exhibit。
Which set of devices contains only intermediary devices？A，B，D, GA，B，E，FC，D, G，IG, H，I, J3Refer to the exhibit。
The headers added at each layer are shown。
Which layer adds the destination and source process ensure that data is delivered to the correct application?physical layerdata link layernetwork layertransport layer4The Layer 4 header contains which type of information to aid in the delivery of data？service port numberhost logical addressdevice physical addressvirtual connection identifier5Which fiber connector supports full—duplex Ethernet？6Which device should be used for routing a packet to a remote network?access switchDHCP serverhubrouter7Refer to the exhibit. Host A sends a frame to host C with a destination MAC address CC. The MAC address for host C is no table of switch SW1。
思科第二学期期末试题及答案
Close WindowAssessment System 1. Assessment Selection 2. Assessment Settings 3. Take Assessment 1Refer to the exhibit. Which summarization should R1 use to advertise its networks to R2? 192.168.1.0/24 192.168.0.0/24 192.168.0.0/22 192.168.1.0/22 2If a router is booting with its default configuration register setting and its NVRAM lacks boot system commands, from try to load the IOS image first? ROM RAM NVRAM f lash flash TFTP server 3Refer to the exhibit. A network administrator adds this command to router R1: ip route 192.168.2.0 255.255.255.0 S0/0/0. result of adding this command? This route is automatically propagated throughout the network. The traffic for network 172.16.1.0 is forwarded to network 192.168.2.0. A static route is established. A static route is established. The traffic for all Class C networks is forwarded to 172.16.1.2. 4Which two technologies can be used in distance vector routing protocols to prevent routing loops? (Choose two.) authentication link-state advertisements h old-down timers hold-down timers Spanning Tree Protocol split horizon 5Refer to the exhibit. What information can be determined from the displayed output? E IGRP packets are waiting to be sent to the neighbors. EIGRP packets are waiting to be sent to the neighbors. The adjacencies between the routers are yet to be established. The IP address 192.168.10.10 is configured at serial interface S0/0/1 of router R2. Router R2 is receiving hello packets from a neighbor with the IP address 192.168.10.10 via the R2 S0/0/1 interf6Which statement is true about the metrics used by routing protocols? A metric is a value used by a particular routing protocol to compare paths to remote networks. A metric is a value used by a particular routing protocol to compare paths to remote networks. A common metric is used by all routing protocols. The metric with the highest value is installed in the routing table. The router may use only one parameter at a time to calculate the metric. 7Which feature of RIPv2 enables it to function as a classless routing protocol? Subnet masks are included in routing updates. Routing updates are triggered by topology changes. Next-hop addresses are included in routing updates. N ext-hop addresses are included in routing updates. Multicast addresses are used to send routing updates. 8Refer to the exhibit. The hosts on the R1 LAN are unable to access the Internet. What is incorrectly configured? the IP address of the Fa0/0 interface at R1 t he IP address of the Fa0/0 interface at R1 the IP address of the S0/0/1 interface at R2 the IP address of the S0/0/0 interface at R1 the subnet mask of the S0/0/1 interface at R2 9Which prompt is used to allow a user to change the IP address of an interface on a router? Router> R outer> Router# Router(config)# Router(config-if)# 10Refer to the exhibit. The interfaces of all routers are configured for OSPF area 0. R3 can ping R1, but the two routeestablish a neighbor adjacency. What should the network administrator do to troubleshoot this problem? Check if the interfaces of the routers are enabled. Check the hello and dead intervals between the routers. C heck the hello and dead intervals between the routers. Check the process ID of both routers. Check if CDP is enabled on all the routers. 11Refer to the exhibit. Which combination of IP address and subnet mask can be used on the serial interface of Route interface in the same network as the serial interface of Router1? IP 172.16.0.18, subnet mask 255.255.255.0 IP 172.16.32.15, subnet mask 255.255.255.240 I P 172.16.32.15, subnet mask 255.255.255.240 IP 172.16.0.18, subnet mask 255.255.255.252 IP 172.16.32.18, subnet mask 255.255.255.252 12Refer to the exhibit. A network engineer has run the show version command on R3. Upon rebooting, R3 does not load configuration settings. What could be the cause of this problem? There is insufficient NVRAM. There is insufficient flash memory. The configuration register is not configured with the default setting. The system image file is not located in NVRAM. 13Refer to the exhibit. On the basis of the show running-config output, which option correctly reflects the routes that will b routing table? 14Refer to the exhibit. Host A is having problems accessing server A. All routers have the same EIGRP configuration a What should be done so that host A can access server A? Add the command n ono auto-summary on all routers. Change the network statements to include a wildcard mask. Adjust the EIGRP hello timers to account for the network delay. Add the command e igrpeigrp log-neighbor-changes on all routers. 15Refer to the exhibit. The network is running the RIP routing protocol. Network 10.0.0.0 goes down. Which statement is the routers in this topology will respond to this event? Router4 will learn about the failed route 30 seconds later in the next periodic update. Split horizon will prevent Router4 from fowarding packets to the 10.0.0.0 network until the holddown timer expire Router5 immediately flushes the unreachable route from its routing table. Router5 will send Router4 a triggered update with a metric of 16 for network 10.0.0.0. 16A network administrator is in charge of two separate networks that share a single building. What device will be require networks and add a common connection to the Internet that can be shared? hub router access point Ethernet switch E thernet switch 17Refer to the exhibit. A network administrator has configured OSPF using the following command: network 192.168.1.32 0.0.0.31 area 0Which router interface will participate in OSPF? FastEthernet0/0 FastEthernet0/1 Serial0/0/0 Serial0/0/1 18Refer to the exhibit. R1 is configured properly for a single area OSPF, and R2 has been recently installed in the netcommands is required to configure a single area OSPF for the networks that are connected to R2? R2(config)# router ospf 1R2(config-router)# network 192.168.2.0 0.0.0.255 area 0R2(config-router)# network 10.1.1.0 0.0.0.3 area 0R2(config)# router ospf 1R2(config-router)# network 192.168.2.0 0.0.0.255 area 0R2(config)# router ospf 2R2(config-router)# network 10.1.1.0 0.0.0.3 area 0R2(config)# router ospf 1R2(config-router)# network 192.168.2.0 0.0.0.255 area 0R2(config-router)# network 10.1.1.0 0.0.0.3 area 1R2(config)# router ospf 1R2(config-router)# network 192.168.2.0 0.0.0.255 area 0R2(config-router)# network 10.0.0.0 0.0.0.3 area 119Which two statements are true for link-state routing protocols? (Choose two.) Routers that run a link-state protocol can establish a complete topology of the network. Routers in a multipoint network that run a link-state protocol can exchange routing tables. Routers use only hop count for routing decisions. The shortest path first algorithm is used. Split horizon is used to avoid routing loops. 20Which candidate route has the longest match for a packet with a destination address of 10.30.16.48? 10.30.0.0/16 10.30.15.0/23 10.30.16.0/24 10.30.16.32/27 10.30.16.32/30 21Which statement is true about the RIPv1 protocol? It is a link-state routing protocol. It excludes subnet information from the routing updates. It uses the DUAL algorithm to insert backup routes into the topology table. It uses classless routing as the default method on the router. 22Which of the following are primary functions of a router? (Choose two.) packet switching microsegmentation domain name resolution path selection flow control 23Refer to the exhibit. Partial results of the show running-config and s how show ip route commands are displayed. Router B rec with a destination address of 10.16.1.97. What will router B do? drop the packet forward the packet via the route to 10.16.1.0 f orward the packet via the route to 10.16.1.64 forward the packet via the route to 10.16.1.64 use the default route 24 What are two ways that a router can learn of the paths to destination networks? (Choose two.) updates from other routers DHCP information broadcasts m anual configuration of routes manual configuration of routes ARP requests from connected routers inspection of the destination IP address in data packets updates from the SMTP management information base 25Refer to the exhibit. Host A is unable to access the Internet. What is the reason for this? The IP address of host A is incorrect. The default gateway of host A is incorrect. The Fa0/1 interfaces of the two routers are configured for different subnets. T he Fa0/1 interfaces of the two routers are configured for different subnets. The subnet mask for the Fa0/0 interface of R1 is incorrect. 26A network administrator is analyzing routing update behavior on a network that has both EIGRP and OSPF configured protocols appear in the output of show ip protocols. However, only EIGRP internal routes appear in the routing tables. correctly explains the scenario? The OSPF protocol has a higher cost than EIGRP. T he OSPF protocol has a higher cost than EIGRPThe EIGRP protocol has a lower metric than OSPF. The EIGRP protocol was configured first on the router. The EIGRP protocol has a lower administrative distance than OSPF. 27Refer to the exhibit. The network has three connected routers: R1, R2, and R3. The routes of all three routers are d are operational and pings are not blocked on this network. Which ping will fail? from R1 to 172.16.1.1 from R1 to 192.168.3.1 from R2 to 192.168.1.1 from R2 to 192.168.3.1 28Refer to the exhibit. A device is required to complete the connection between router R1 and the WAN. Which two de this? (Choose two.) a CSU/DSU device a modem a n Ethernet switch an Ethernet switch a hub a bridge 29 In which situation would a default static route be recommended? when connecting an edge router to the Internet w hen variable length subnet masking is in effect when variable length subnet masking is in effect when there is more than one valid route for a destination network when a destination network has a larger mask than any routes in the routing table 30 Two routers need to be configured within a single OSPF area. Which two components need to be configured on boththis? (Choose two.) t he same process ID the same process ID the same area ID network addresses and wildcard masks the same router ID the same loop back address 231Refer to the exhibit. What is the meaning of the highlighted value 120? It is the metric that is calculated by the routing protocol. It is the value that is used by the DUAL algorithm to determine the bandwidth for the link. It is the administrative distance of the routing protocol. It is the hold-down time, measured in seconds, before the next update. 32Refer to the exhibit. A router learns a route to the 192.168.6.0 network, as shown in the output of the show ip rip database However, upon running the show ip route command, the network administrator sees that the router has installed a diff command, the network administrator sees that the router has installed a diffe 192.168.6.0 network learned via EIGRP. What could be the reason for the missing RIP route? Compared to RIP, EIGRP has a lower administrative distance. Compared to EIGRP , RIP has a higher metric value for the route. Compared to RIP , the EIGRP route has fewer hops. Compared to RIP , EIGRP has a faster update timer. 33 Which mechanism helps to avoid routing loops by advertising a metric of infinity? route poisoning split horizon hold-down timer triggered updates 34 A network administrator must use the subnet 172.16.128.0/18 to create 6 additional subnets each containing up to 20LANs. Which subnet mask should the administrator use to create the new subnets? 255.255.224.0 255.255.240.0 255.255.248.0 255.255.252.0 35 A technician configures the Fa0/0 interface on a router with ip address 192.168.3.5 255.255.255.252. What additional com. What additional com issued by the technician to activate the interface to forward traffic? Router(config-if)# exitRouter(config-if)# no shutdownRouter(config-if)# clock rateRouter# copy running-config startup-config36 Because of a topology change, the next hop IP address in the current static route must be reconfigured. How can a altered to accommodate a topology change? Keep the existing static route and configure a new static route with the correct next hop IP address. Negate the existing static route and configure a new static route with the correct next hop IP address. D o nothing. The existing static route will automatically update the next hop entry with the new IP address. Do nothing. The existing static route will automatically update the next hop entry with the new IP address. Keep the existing static route, reload the router, and configure a new static route with the correct next hop IP a37Refer to the exhibit. What needs to be done to allow these two routers to connect successfully? Add a clock rate to S0/0/0 on R1. Add an interface description to S0/0/1 on R2. C hange the serial interface on R2 to S0/0/0 so that it matches R1. Change the serial interface on R2 to S0/0/0 so that it matches R1. Change the IP address of S0/0/1 on R2 so that it is in the same subnet as R1. 38Refer to the exhibit. The network administrator has run the following command on R1. R1(config)# ip route 192.168.2.0 255.255.255.0 172.16.1.2What is the result of running this command? Traffic for network 192.168.2.0 is forwarded to 172.16.1.2. This route is automatically propagated throughout the entire network. Traffic for all networks is forwarded to 172.16.1.2. The command invokes a dynamic routing protocol for 192.168.2.0. 39 Why is fast convergence desirable in networks that use dynamic routing protocols? Hosts are unable to access their gateway until the network is converged. Routers will not allow packets to be forwarded until the network is 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. 40Refer to the exhibit. When all of the commands that are shown in the exhibit are entered at the correct router promp the router? name cisco router hostname 41Refer to the exhibit. Packets destined to which two networks will require the router to perform a recursive lookup? (C10.0.0.0/8 64.100.0.0/16 128.107.0.0/16 172.16.40.0/24 192.168.1.0/24 192.168.2.0/24 42Refer to the exhibit. A router interface is configured with the command ip address 172.16.3.31 255.255.192.0. Which set o. Which set o values would allow a computer that is connected to the router interface to communicate with remote networks? A: 172.16.3.254 A: 172.16.3.254 B: 255.255.192.0 C: 172.16.3.31 A: 172.16.3.31 B: 255.255.192.0 C: 172.16.3.255 A: 172.16.3.254 B: 255.255.255.0 C: 172.16.3.31 A: 172.16.3.31 B: 255.255.255.0 C: 172.16.3.1 43Which three statements are true regarding the encapsulation and de-encapsulation of packets when traveling through three.) The router modifies the TTL field, decrementing it by one. The router changes the source IP to the IP of the exit interface. The router maintains the same source and destination IP. The router changes the source physical address to the physical address of the exit interface. The router changes the destination IP to the IP of the exit interface. The router sends the packet out all other interfaces, besides the one it entered the router on. 44Refer to the exhibit. Which three statements are true of the routing table for Router1? (Choose three.) The route to network 172.16.0.0 has an AD of 156160. Network 192.168.0.16 can best be reached using FastEthernet0/0. The AD of EIGRP routes has been manually changed to a value other than the default value. Router1 is running both the EIGRP and OSPF routing process. Network 172.17.0.0 can only be reached using a default route. No default route has been configured. N o default route has been configured. 45Refer to the exhibit. Which route will be installed in the routing table on R1 to forward traffic from PC1 to the web s the static route the route learned via OSPF the route learned via EIGRP both routes learned via OSPF and EIGRP 46Refer to the exhibit. Based on the partial output in the exhibit, why can users establish a console connection to this r a password? The login command was not entered on the console line. The enable password should be an enable secret password. No username and password combination has been configured. Console connections cannot be configured to require users to provide passwords. 47Refer to the exhibit. Which path will traffic from the 172.16.1.0/24 network take to get to the 10.0.0.0/24 network? ADC ABC It will load balance the traffic between ADC and ABC It will send the traffic via ABC, and will use ADC as a backup path only when ABC fails. 48A router learns about network 192.168.10.128/27 from multiple sources. Which option represents the best route and w routing table? S 192.168.10.128/27 [1/0] via 192.168.10.226 R 192.168.10.128/27 [120/2] via 192.168.10.226, 00:00:14, Serial0/0/0 O 192.168.10.128/27 [110/1563] via 192.168.10.226, 00:00:09, Serial0/0/0 D 192.168.10.128/27 [90/21026560] via 192.168.10.226, 00:00:16, Serial0/0/0 49Refer to the exhibit. R1 and R2 are adjacent routers both running RIP. All interfaces on both routers are correctly cothe routing table. What is the likely cause? The adjacent interfaces are passive. The distance of 120 exceeds 15 hops. R2 will not accept version 1 updates from R1. Routes are being summarized by R1 but not by R2. 50It is saved in the topology table for use if the primary route fails. It may be backed up by a feasible successor route. It is used by EIGRP to forward traffic to the destination. It is flagged as active in the routing table. After the discovery process has occurred, the successor route is stored in the neighbor table. 51Refer to the exhibit. PC1 is unable to access the Internet. What is the cause of the problem? An incorrect IP address is configured between the two routers. No static route is configured on Router2. A routing loop has occurred. No routing protocol is configured on either of the two routers. 52Refer to the exhibit. A technician has configured the interfaces on the Router, but upon inspection discovers that inte FastEthernet0/1 is not functioning. Which action will most likely correct the problem with FastEthernet0/1? A clock rate should be added to the interface configuration. The subnet mask should be added to the interface configuration. An interface description needs to be added to the interface configuration. The no shutdown command needs to be added to the interface configuration. 。
思科 期末考试答案
关闭窗口考试系统考试浏览器 - ENetwork Final Exam - CCNA Exploration: Network Fundamentals (版本下面是考试的考试试题以及与题目关联的评分规则。
思科网络技术学院的内容是受到版权保护的,禁止一切未经授权的张贴,分发或共享本考试的内容.1下列哪一个 OSI 层负责管理数据段？应用层表示层会话层传输层2请参见图示。
图中所示为客户端之间发送电子邮件的过程。
以下哪一列表正确地标识了图中各编号阶段使用的组件或协议？3第 4 层报头包含帮助数据传输的哪一类信息？服务端口号主机逻辑地址设备物理地址虚拟连接标识符4哪个 OSI 层提供面向连接的可靠数据通信服务？应用层表示层会话层传输层网络层5当 OSI 模型下层执行无连接协议时，通常使用什么来确认数据已收到并请求重传丢失的数据？IPUDP以太网无连接确认面向连接的上层协议或服务6下列哪三项是 CSMA/CD 的特征？（选择三项。
）设备会侦听介质，并且仅当无法检测到介质上存在其它信号时才会传输数据。
介质上的所有设备均可侦听所有通信。
设备根据配置的优先级来进行通信。
发生冲突后，引起冲突的设备会优先尝试传输数据。
发生冲突时，所有设备会在一段时间内停止传输数据，该段时间的长度随机决定。
CSMA/CD 使用令牌系统来避免冲突。
7在封装过程中，传输层添加什么标识符？源 IP 地址和目的 IP 地址源 MAC 地址和目的 MAC 地址源端口号和目的端口号源通道标识符和目的通道标识符8数据链路层有哪两项功能？（选择两项）分割和记录数据。
在源主机和目的主机上运行的程序之间进行数据交换。
控制数据如何传递到介质中。
生成信号以表示每个帧中的比特。
使用帧头和帧尾封装每个数据包，以便在本地介质中进行传输。
9请参见图示。
网络中的主机 A 和 B 正在传输层交换数据段。
下列关于此交换的陈述，哪两项是正确的？（选择两项）主机 A 正在使用 FTP 向主机 B 传输文件。
思科第一学期期末考试最新考题CCNA1
1Refer to the exhibit. Which Layer 2 protocol could be used inside nework A and network C?IPTCPUDPEthernet2Refer to the exhibit. Which set of devices contains only intermediary devices?A, B, D, GA, B, E, FC, D, G, IG, H, I, J3Refer to the exhibit. The headers added at each layer are shown. Which layer adds the destination and source process num ensure that data is delivered to the correct application?physical layerdata link layernetwork layertransport layer4The Layer 4 header contains which type of information to aid in the delivery of data?service port numberhost logical addressdevice physical addressvirtual connection identifier5Which fiber connector supports full-duplex Ethernet?6Which device should be used for routing a packet to a remote network?access switchDHCP serverhubrouter7Refer to the exhibit. Host A sends a frame to host C with a destination MAC address CC. The MAC address for host C is no table of switch SW1. How will SW1 handle the frame?Switch SW1 will drop the frame.Switch SW1 will forward the frame to host C.Switch SW1 will flood the frame out all ports.Switch SW1 will flood the frame out all ports except port Fa0/1.8Refer to the exhibit. A network technician has made several changes to R1 since the configuration has last been saved. Th configuration did not produce the desired changes. The technician wants to store a backup copy of the saved configurationserver before reloading. Which action will cause the unmodified data to be saved on the TFTP server?9Which three statements are true about network layer addressing? (Choose three.)It uniquely identifies each host.It assists in forwarding packets across internetworks.It uses a logical 32-bit IPv4 address.It is not a configurable address.It is a physical address.It identifies the host from the first part of the address.10What is the result of using the clock rate 56000 command at the serial interface of the router?The interface is configured as a DCE device.The interface timers are cleared.The FastEthernet interface is made to emulate a serial interface by assigning it a timing signal.The IP address for the serial interface is configured.11Examine the graphic with current configurations. Host A in the Clerical office failed and was replaced. Although a ping to 12 successful, the replacement computer cannot access the company network. With proxy ARP disabled on the Fa0/0 interfac York router, what is the likely cause of the problem?network card failurenetwork cables unpluggedIP address incorrectly enteredsubnet mask incorrectly entered12As network administrator, what is the subnet mask that allows 510 hosts given the IP address 172.30.0.0?255.255.0.0255.255.248.0255.255.252.0255.255.254.0255.255.255.0255.255.255.12813Which OSI layer uses a connection-oriented protocol to ensure reliable delivery of data?application layerpresentation layersession layertransport layer14 A network has grown too large for technicians to configure network addresses and hosts files for name resolution. Which twlayer services should be added to the server to allow these needs to be satisfied dynamically? (Choose two.)DNSFTPDHCPHTTPSMTP15Refer to the exhibit. Host A wants to access the Internet. Which combination of a Layer 2 address and a Layer 3 address w access from host A?Destination MAC: 0030.8596.DE83 Default gateway: 209.165.202.130Destination MAC: 0030.8596.DE82 Default gateway: 172.16.9.2Destination MAC: 0030.8517.44C4 Default gateway: 172.16.1.1Destination MAC: 0030.8517.44C4 Default gateway: 209.165.202.13016 A network administrator is asked to design a new addressing scheme for a corporate network. There are 60 users in the mausers in the branch office, 28 users in manufacturing, 12 in the sales office, and 4 users in the research office. Which VLSM scheme that uses the 192.168.88.0/24 network will fulfill the requirements while wasting the fewest addresses?192.168.88.0/26 main192.168.88.64/26 manufacturing192.168.88.96/27 sales192.168.88.128/28 research192.168.88.0/26 main192.168.88.128/27 manufacturing192.168.88.160/28 sales192.168.88.176/29 research192.168.88.0/27 main192.168.88.64/28 manufacturing192.168.88.80/29 sales192.168.88.88/30 research192.168.88.0/27 main192.168.88.80/28 manufacturing192.168.88.96/29 sales192.168.88.104/30 research17Which physical connector type is used for a serial V.35 connection to the CSU/DSU?18Refer to the exhibit. Which two facts can be determined about the topology? (Choose two.)Four collision domains are present.One logical network is represented.Two broadcast domains are present.Three networks are needed.Three logical address ranges are required.19What are three characteristics of CSMA/CD? (Choose three.)It monitors the media for presence of a data signal.After detecting a collision, hosts can resume transmission after a random timer has expired.A jam signal is used to ensure that all hosts are aware that a collision has occurred.Devices can be configured with a higher transmission priority.Data is transmitted only when the data signal is present.It uses a token system to avoid collisions.20Refer to the exhibit. The serial interface of the router was configured with the use of the commands that are shown. The rou ping the router that is directly connected to interface serial 0/0/0. What should the network technician do to solve this probleConfigure the description at interface serial 0/0/0.Configure an IP address on interface serial 0/0/0.Remove the no shutdown command at interface serial 0/0/0Reboot the router.21Which OSI layer uses the header information to reassemble the data segments into streams?application layernetwork layerpresentation layersession layertransport layer22Refer to the exhibit. The NAT functionality of the router is enabled to provide Internet access to the PC. However, the PC is access the Internet. Which IP address should be changed to 209.165.201.1 to enable the PC to access the Internet?192.168.1.191192.168.1.101192.168.1.1192.168.1.25423Refer to the exhibit. A technician uses the nslookup command on the PC and views the output that is displayed in the exhib IP address of the primary domain name server used by the host?10.10.10.32192.168.1.5192.168.1.99192.168.2.10024Which memory contents will change as a result of using the Router# erase startup-config command on a router?RAMROMflashNVRAM25While configuring a router, a network technician wants to name the router. Which prompt should the technician see when e hostname command?Router>Router#Router(config)#Router(config-line)#26Refer to the exhibit. The PC, the routing table of which is displayed, is configured correctly. To which network device or inte IP address 192.168.1.254 belong?PCswitchrouter interface fa0/0router interface fa0/127Refer to the exhibit. A network administrator is troubleshooting a link that is down between Router1 and Router2. To correc which wire pairs need to be switched on one of the Ethernet cable ends?pair 1 and pair 2pair 1 and pair 3pair 2 and pair 3pair 2 and pair 428Refer to the exhibit. A PC is connected to a network. Which action will verify that the PC can communicate with its default gUse the ping 127.0.0.1 command.Use the ipconfig command.Use the ipconfig/all command.Use the ping 10.0.0.254 command.29Refer to the exhibit. Host B was powered off. What change will occur in the MAC table of the switch?The table will remain unaffected.The switch will remove the MAC address at Fa0/19.The switch will retain the MAC address until host B is powered on again.The switch will rebuild the MAC table by assigning the FFFF.FFFF.FFFF address to port Fa0/19.30What information is contained in the header of Layer 3 to help data delivery?port numberdevice physical addressdestination host logical addressvirtual connection identifier31 A network technician is tasked with setting up a network for six users, but the users should be able to use their accounts toany of the six computers. What type of network should be used?workgroupP2P applicationspeer-to-peer networkclient-server network32Refer to the exhibit. A web browser is running on host PC1 with an IP address 10.10.2.2/24. A dynamic port number of 4915 to the browser. The browser sends a request for a web page to the web server with an IP address 192.168.1.254/24. Which true?The session is established using TCP, and the socket number for the web server is 192.168.1.254: 80.The session is established using TCP, and the socket number for the web server is 192.168.1.254: 49152.The session is established using UDP, and the socket number for the web server is 192.168.1.254: 80.The session is established using UDP, and the socket number for the web server is 192.168.1.254: 49152.33Refer to the exhibit. An administrator on PC1 wants to view some HTML code from a web page housed on the web server. application will allow this request to be started?34Refer to the exhibit. What is required on host A for a network technician to create the initial configuration on Router1?an FTP clienta Telnet clienta terminal emulation programa web browser35What are two characteristics of the data link layer? (Choose two.)It segments and reorders the data.It exchanges the frames between nodes.It defines the method by which network devices place data onto the media.It manages the transfer of data between the processes that run on each host.It retrieves signals from the media and restores them to their bit representations.36 A network administrator wants to restrict access to the router privileged EXEC mode. Which password should the administrenableauxconsoleVTY37Which three IPv4 addresses represent a broadcast for a subnet? (Choose three.)172.16.4.63 /26172.16.4.129 /26172.16.4.191 /26172.16.4.51 /27172.16.4.95 /27172.16.4.221 /2738Refer to the exhibit. Host X is unable to communicate with host Y. Which command can be run at host X to determine which device is responsible for this failure?telnet 192.168.1.1ping 192.168.1.1ftp 192.168.1.1tracert 192.168.1.139Refer to the exhibit. Which option shows the correct topology given the configuration of Router1?40If an administrator wished to return a router to the default state, what additional step must be taken after issuing the comma start-up config?Reload the device.Issue the command copy running-config start-up config.Perform a show running-config to verify that the file was removed.Enter the interface commands to allow the device to connect to the network.41By using the ipconfig command, a network administrator determines that a workstation has the address 192.168.3.38 with the subnet mask. To what network does the workstation belong?192.168.3.8192.168.3.16192.168.3.24192.168.3.3242Which statement is true about router hostnames?A hostname should be unique on each router.A router hostname cannot contain capital letters.A router hostname is configured in privileged executive mode.A router hostname must be created before any other configurations can be added to the device.43 A user types the enable command. What task can be performed at the privileged EXEC mode?Configure the device.Configure individual interfaces.Configure individual terminal lines.Issue show and debug commands.44Refer to the exhibit. Which logical topology describes the exhibited network?starringpoint-to-pointmulti-access45Refer to the exhibit. A user wants to access the Internet from the PC. A part of the running configuration of the router is sho default gateway IP address should be configured at the PC to enable this access?10.1.192.110.1.192.210.1.192.54192.31.7.146Which statement is true about the ICMP protocol?It is an application layer protocol.It is designed to make IP a reliable protocol.It is often filtered out of networks for security purposes.If a host does not respond to an ICMP echo request, the host is not functioning.47Refer to the exhibit. At which OSI layer is serial interface 0/0/1 experiencing problems?Layer 1Layer 2Layer 3Layer 448Refer to the exhibit. The host was disconnected from switch 2 and connected to switch 1. Which combination of IP address, and default gateway should be assigned to this host to allow it to function in the network?IP address: 10.10.9.37 Subnet mask: 255.255.255.240 Default gateway: 10.10.9.35IP address: 10.10.9.37 Subnet mask: 255.255.255.224 Default gateway: 10.10.9.35IP address: 10.10.9.29 Subnet mask: 255.255.255.248 Default gateway: 10.10.9.35IP address: 10.10.9.32 Subnet mask: 255.255.255.224 Default gateway: 10.10.9.35IP address: 10.10.9.37 Subnet mask: 255.255.255.224 Default gateway: 196.1.105.6IP address: 10.10.9.63 Subnet mask: 255.255.255.224 Default gateway: 10.10.9.3549Refer to the exhibit. The diagram represents the process of sending email between clients. Select the list below that correc the component or protocol used at each numbered stage of the diagram.1.MUA2.MDA3.MTA4.SMTP5.MTA6.POP7.MDA8.MUA1.MUA2.POP3.MDA4.SMTP5.MTA6.MDA7.SMTP8.MUA1.MUA2.POP3.SMTP4.MDA5.MTA6.SMTP7.POP8.MUA1.MDA2.SMTP3.MTA4.SMTP5.MTA6.MUA7.POP8.MDA1.MUA2.SMTP3.MTA4.SMTP5.MTA6.MDA7.POP8.MUA50What is the Cisco IOS?system software for Cisco devicesRead Only Memory in Cisco devicesnon-volatile storage for device configurationsan initial operating system that is used for boot functions。
《CISCO路由器配置》期末试题
《CISCO路由器配置》2009上半年～2011上半年期末试题一、单选题1.以太网的MAC地址有( A )位二进制表示。
A．48 B．32 C．46 D．242.以太网数据链路层采用( C )协议A．PPP B．FRC．CSMA/CD D.X．253.( B )是A类IP地址的子网掩码A. 255.255.255.0B.255.0.0.0C. 255.255.0.0D. 255.255.255.1924.( C )是B类IP地址的子网掩码A．255.255.255.0B．255.0.0.0C．255.255.0.0D．255.255.255.1925.( A )是C类IP地址的子网掩码A. 255.255.255.0B. 255.0.0.0C. 255.255.0.0D. 255.255.255.1926.( A )协议是通过IP地址找MAC地址的地址解析协议A. ARPB. RSAC. RARPD. IDEA7.( B )不是TCP/IP模型的层A.网络接口层B.数据链路层C.网络互联层D.传输层和应用层8.OSI参考模型中的应用层，表示层，会话层对应TCP/IP模型的( D ) A．网络接口层B．传输层C．网络互联层D．应用层9.( D )不是Cisco路由器的启动模式A．SETUP B. ROM MonitorC. RXBootD.用户模式10.Cisco路由器使用( C )指令最终进入到全局配置模式A．Enabje B，disableC.confgure terminalD.Hostname11.Cisco路由器使用( D )指令查看命令历史缓存大小A、show historyB、display historyC、display teminal D. show terminal12.Cisco路由器接口配置IP地址用( A )指令进行A. ip address <IP地址> <子网掩码> [secondary]B．ip address <子网掩码> <IP地址> [secondary]C. <IP地址> <子网掩码> ip address [secondary]D．ip address [secondary] <IP地址> <子网掩码>13.下列哪个指令是Cisco路由器用来配置接口工作模式的( A )A. full-duplexB.hostnameC.DescriptionD.Configure terminal14.( C )协议是通过MAC地址找IP地址的反地址解析协议A. ARPB. RSAC. RARPD. IDEA15.( D )不可以用来管理、配置Cisco路由器A. Console口B. AUX口C. TelnetD. FTP16.PPP协议不具有( D )功能A.身份认证B.错误检测 c.多连接 D.同步并行17.( A )指令出来测试网络层连接情况A. traceB. undoC. showD. display18.( A )指令用来显示路由表A.show ip routeB.show ip protocolC. show ip-routeD.show ip-protocol19.ACL做流量过滤时一般放在( B )A.入站接口B.出站接口C.个人计算机上D.服务器计算机上20.网络管理不包括( D )A.配置管理、记账管理B.性能管理、故障管理C.安全管理D.人员管理21.以下哪个不是局域网的拓扑结构( D )A、总线型B、环形C、星形D、超级立方体形22.( A )不是路由协议。
电大、自考、考研、大学期末、职称考试、招聘《CISCO路由器配置》复习题
电大、自考、考研、大学期末、职称考试、招聘《CISCO路由器配置》复习题一、选择题1．X.25分组交换网络是一种（）的共享式传输服务网络。
A．面向无连接 B．局域网C．面向连接D．城域网2、Cisco2912交换机工作在OSI体系的哪一层（）A．物理层 B. 数据链路层C．网络层 D. 传输入层3、给路由器命名的IOS命令是（）A．name B. hostnameC．admin D. root4、进入路由器特权模式的命令是( )A．enable B. config terminalC．super D. administrator5、进入百兆以太口0/1的命令为（）A．interface fastethernet 0/1 B. interface Ethernet 0/1C．interface fastethernet 1/0 D. interface Ethernet 1/06、进入路由器串口0的命令是（）A．int bri0 B. int s0C．int e0 D. int f07、新路由器与交换机的初始配置接口为( )A．Bri B. AUXC．AUI D. Console8、不同厂商的路由器通过串行口互连应使用的二层协议为( )A．PPP B. HDLCC．SNMP D. OSPF9、使用路由器可以把内网私有地址转换后出去，要实现该操作必须在路由器上做( )A．PPP B. Frame-relayC．SNMP D. NAT/PAT10、路由器的原始配置寄存器的值为（），修改该值可以达到破解密码的效果。
A．0x2101 B. 0x2102C．0x2141 D. 0x214211、路由器和交换机的console线为( )A．直通线 B. 交叉线C．全反线 D. 568A/568B线12、在路由器上接普通Modem的接口是( )A．Bri B. AUXC．AUI D. Console13、路由器上存放路由配置文件的内存为( )A．NVRAM B. RAMC．ROM D. Flash ROM14、正在路由器上起作用的配置文件为（）A．tftp B. running-configC．flash D. startup-config15、买来后无需配置就能使用的网络设备是（）A．交换机 B. 路由器C．防火墙 D. 网关16、只能工作在物理层的网络设备是( )A．交换机 C. HUBC．路由器 D. 防火墙17、要使得连在同一交换机上同一逻辑网段的计算机不能互相访问的技术为( )A．单臂路由 B. 子接口C．VLAN D. ISDN18、从路由器的接口模式直接退到特权模式的路由命令是( )A．cd \ B. quitC．exit D. end19、启用路由器或交换机某接口的命令是（）A．shutdown B. no shC．active D. enable20、保存路由器的配置使用的路由命令是（）A．write B. copy startup-config running-configC．Save D. copy tftp running-config21、路由器工作在OSI体系的哪一层（）A．物理层 B. 数据链路层C．网络层 D. 传输入层22．路由器内部由（）、各种存储器以及各种接口电路等组成。
期末复习题参考答案
1. 请参见图示。
所有交换机都配置有默认的网桥优先级。
如果所有链路都在相同的带宽下运行，哪两个端口将成为 STP 根端口？（选择两项。
）交换机 A 的 Fa0/1 接口交换机 A 的 Fa0/2 接口交换机 B 的 Fa0/1 接口交换机 B 的 Fa0/2 接口交换机 C 的 Fa0/1 接口交换机 C 的 Fa0/2 接口2. 下列有关交换机上无标记帧的说法中，哪两项正确？（选择两项。
）无标记帧无法通过接入端口。
无标记帧无法通过中继端口。
所有通过中继端口的帧都是无标记帧。
无标记帧可最大程度降低因检查 VLAN ID 标记而造成的延迟。
在中继端口处接收到的无标记帧是本征 VLAN 的成员。
3. 下列哪三种说法与 PPP 封装和 CHAP 身份验证相关？（选择三项。
）CHAP 以明文发送口令。
CHAP 通过重复询问进行检验。
PPP 封装是在接口模式下配置的。
CHAP 通过双向握手建立链路。
PPP 封装是 Cisco 路由器的串行接口采用的默认封装。
CHAP 使用基于 MD5 哈希算法的询问/响应方法。
4. 某组织计划通过增加五个分支机构来扩张规模。
扩张后，该组织需要将新建的分支机构安全、不间断且同时地连接到中心办公室。
中心办公室路由器上只有一个可用端口。
在这种情况下，可以使用哪种 WAN 技术？PPPISDN帧中继模拟拨号5. 哪两种说法正确描述了 RSTP？（选择两项。
）是一种 Cisco 专有协议可在不到 1 秒的时间内重新计算生成树。
需要交换机端口上具有 PortFast 和 UplinkFast 功能。
支持四种状态：阻塞、侦听、学习和转发。
要求交换机之间采用全双工、点对点连接，以便达到最快的重新计算速度。
6. 哪两种说法正确描述了 RIPv1 和 RIPv2？（选择两项。
）两种协议都会将整个路由表从所有参与的接口广播到。
两种协议都会每隔 30 秒从所有活动接口向外通告路由更新。
两种协议都具有相同的管理距离值 120。
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c i s c o期末复习题(含答案)(一)1一个销售代表准备从酒店使用 Internet 向公司总部发送敏感信息。
旅行前，IT 工作人员进行了必要工作以允许其安全Internet。
为该销售代表实施了什么解决方案VPN帧中继带有 CHAP 身份验证的 PPP带有 PAP 身份验证的 PPP2. 请参见图示。
网络 172.30.20.0/24 中的用户无法访问网络 192.168.0.0/23 中的任何服务器。
给定网络拓扑和 OSPF 配置，此网中存在哪两个问题？（选择两项。
）在所有三台路由器间存在路由环路。
缺少一条 network 语句。
网络 172.30.20.0 的通配符掩码不正确。
OSPF 区域配置不正确。
对于网络 192.168.0.0 来说，子网掩码 /23 无效。
3. 请参见图示。
网络管理员必须为 ISP 手动总结 POP 路由器上的所有 IP 地址。
下列哪项是正确的总结地址？192.168.0.0/22192.168.0.0/23192.168.0.0/24192.168.0.0/254. 在企业网络中实施 VLAN 有哪两点好处？（选择两项。
）避免使用第 3 层设备提供广播域分段功能允许广播数据从一个本地网络传播到另一个本地网络允许对设备进行逻辑分组而不考虑物理位置通过确保环境中无环路等措施来避免诸如广播风暴等问题5. 如果为 PPP 配置了身份验证协议，则何时对客户端或用户工作站进行身份验证？在建立链路之前在建立链路的过程中在开始配置网络层协议之前在配置完网络层协议之后6. 一家公司使用 B 类 IP 编址方案，预计需要 150 个网络。
以下哪一子网掩码适用于该网络配置？255.255.0.0255.255.240.0255.255.254.0255.255.255.0255.255.255.128255.255.255.1927. 一位销售代表正在使用无线连接进行 VoIP 通话。
语音数据包将通过哪种协议来传输？TCPUDPPPPHDLC8. 在企业边缘进行的服务可为公司带来什么好处？与服务器群通信更快抵抗恶意攻击的安全性更高与 Internet 目的地通信更快通过 VLAN 和冗余中继链路增强性能和可靠性9. 网络工程师把当前网络统计信息与之前的基线比较后，发现通向外联网的不必要流量明显增多。
哪两个步骤可简化管理并控制不必要的流量？（选择两项。
）在分布层定义 ACL 以隔离数据包在企业边缘处的路由器上添加 ACL 以拦截通信部署第 3 层交换机以限定广播通信将远程位置直接连接到内部网使用相同的默认网关配置所有主机，以消除不必要的广播通信部署一台核心 ISP 路由器以减轻因确定路径而引入的延时10. 下列关于 EIGRP 表的说法中哪两项正确？（选择两项。
）可行后继路由可在拓扑表中找到。
只有后继路由可在拓扑表中找到。
拓扑表会显示路由是处于被动状态还是主动状态。
路由表会显示路由器建立相邻关系以来经过的时间。
相邻设备表会显示相邻的所有 Cisco 设备。
管理距离在相邻设备表中显示为一列。
11. 请参见图示。
图中的所有路由都可供路由器进行选择。
哪两条路由将被放入路由表中？（选择两项。
）ABCDEF12. 请参见图示。
网络管理员将命令ip route 10.10.4.16 255.255.255.248 s0/0/1输入路由器中。
此配置的结果是什么？一条指向 10.10.4.16/29 的静态路由将被放入路由表中。
如果 FastEthernet0/1 接口关闭，则一条指向 10.10.4.16/29 的静态路由将被放入路由表中。
仅当指向 10.10.4.0 的路由被删除时，一条指向 10.10.4.16/29 的静态路由才被放入路由表中。
不会向路由表中放入静态路由，原因在于已经存在一条包含目的网络的 RIP 路由。
13. 请参见图示。
路由表中将显示哪些路由？R 10.10.4.0/24 [120/1] via 10.10.10.1, 00:00:12, FastEthernet0/1R 10.10.4.0/24 [120/1] via 10.10.20.1, 00:00:12, FastEthernet0/0R 10.10.4.0/24 [120/2] via 10.10.20.1, 00:00:12, FastEthernet0/0R 10.10.4.0/24 [120/3] via 10.10.30.1, 00:00:12, FastEthernet1/0R 10.10.4.0/24 [120/1] via 10.10.30.1, 00:00:12, FastEthernet1/014. 请参见图示。
128.107.0.0 网络的 Null0 路由表示什么？已定义的子路由已定义且源自某物理接口的父路由用于通告的总结路由，不是实际路径在路由器上使用no auto-summary命令的结果15. OSPF 路由协议身份验证使用 MD5 验证时，下列有关密钥的说法中哪两项正确？（选择两项。
）密钥以明文形式在路由器之间传递。
密钥用于帮助生成验证用的加密数字。
密钥以加密形式在路由器之间传递。
密钥永远不会在网络上传输。
数据包嗅探器可以捕获密钥。
16. 请参见图示。
该网络使用的是 OSPF 路由协议。
网络管理员发出show ip ospf neighbor命令检查运行状态。
下列哪项说法正确？RB 的优先级值最小。
RC 和 RD 在网络中的路由器 ID 最小。
RA 已与所有邻居路由器建立起邻接关系。
RA 和 RB 无法建立邻接关系，因为它们处于双向状态。
17. 请参见图示。
从图中所示的输出可得出哪两条结论？（选择两项。
）目的 IP 地址为 172.20.1.14 的数据包将通过 Serial 0/1/0 接口离开路由器。
EIGRP 的默认管理距离已被更改。
可通过两条开销相等的路由达到网络 172.20.1.4。
目的 IP 地址为 172.16.1.5 的数据包将被丢弃。
连接到 Serial 0/1/1 接口的路由器正在通过 EIGRP 向此路由器通告 4 条各不相同的路由。
18. 请参见图示。
图中的网络配置有 RIPv2。
网络中的主机可访问全部内部网络，但无法访问 Internet。
图中所示的命令应该添加到哪台路由器，才能让网络中的所有主机能访问 Internet？R1R2R3ISP19. 请参见图示。
假设启用了 RIPv1 路由协议且每台路由器上均已正确配置了所有网络，则下列哪种说法正确？从 H1 发往 H2 的所有数据包都会到达 H2。
从 H1 发往 H2 的所有数据包都不会到达 H2。
从 H1 发往 H2 的流量中，约有一半会到达 R3。
从 H1 发往 H2 的部分数据包将被发送到网络 192.168.3.64/26 所连接的交换机。
20. 请参见图示。
从此命令的输出中可获得哪两点信息？（选择两项。
）172.16.16.0/20 是手动总结的路由。
因为禁用了默认总结，所以会通告所有子网。
输出表明 EIGRP 只会通告处于相同 AS 中的网络。
网络 172.16.1.0/24 直接连接到生成此输出的路由器。
Null0 接口表明这不是一条真实路径，而是用于通告的总结路由。
21. 请参见图示。
假设所有三台路由器均配置有 EIGRP 路由协议并共享信息，则从该 show 命令输出中可获得什么信息？路由器 B 与路由器 A 和路由器 C 建立了 EIGRP 相邻关系。
路由器 B 拥有完全收敛的拓扑表。
路由器 B 未与路由器 A 建立相邻关系。
路由器 B 未与路由器 C 建立相邻关系22. 在企业网络中可通过哪两种方式建立 VLAN 成员资格？（选择两项。
）手动将交换机端口配置为属于 VLAN允许用户通过 GUI 菜单选择特定的 VLAN将交换机配置为允许基于 NetBIOS 关联确立 VLAN 成员资格使用访问列表指定将哪些设备放入特定 VLAN。
在 VLAN 管理策略服务器数据库中将 MAC 地址与特定 VLAN 关联手动将主机设备配置为属于 VLAN23. 请参见图示。
网络管理员刚刚在 HQ 路由器上配置了一条默认路由。
为使 OSPF 网络中的所有路由器均具有到 Internet 的路由，应该采取下述哪两项措施？（选择两项。
）必须在 OSPF 路由器上设置最后选用网关。
HQ 会自动将默认路由传播到其它每台 OSPF 路由器。
HQ 将向 DR 和 BDR 发送默认路由信息，以便二者将该信息发布给其它路由器。
每台路由器都必须配置有到 64.104.22.16/28 网络的静态路由。
HQ 必须配置有default-information originate命令。
每台路由器必须在 OSPF 配置中包含语句network 64.104.22.16 0.0.0.15 area 0。
24. 请参见图示。
网络中启用了 OSPF，并且网络现在已完全收敛。
哪两台路由器将被指定为 DROTHER 路由器？（选择两项。
）R1R2R3R425. 公司总部使用静态路由连接三个分部。
为 WAN 连接使用静态路由有哪两点好处？（选择两项。
）静态路由更安全。
静态路由收敛更快。
静态路由的管理距离比动态路由协议更高。
仅当 WAN 连接的带宽变化时，才需要调整静态路由的度量。
在内部网关协议中，静态路由更稳定，更不易受到网络更改的影响。
26. 请参见图示。
Internet 接入对图中的公司网络至关重要。
Internet 接入由两家 ISP 提供。
ISP1 是主提供商，ISP2 是后备提供商。
网络管理员将 BorderR 配置为边界路由器，从而使日程运作中所有 Internet 流量都经过 ISP1。
然而，如果通向 ISP1 的链路发生故障，BorderR 会自动将 Internet 流量转发给ISP2。
管理员配置了两条默认路由：BorderR(config)# ip route 0.0.0.0 0.0.0.0 192.168.100.1 200BorderR(config)# ip route 0.0.0.0 0.0.0.0 172.16.1.1然而，当管理员发出show ip route命令检验配置时，路由表中只出现了第二条默认路由。
为什么不显示第一条默认路由？第一条配置命令覆盖了第二条命令。
如果出现发往网络 192.168.100.0 的流量，则第一条默认路由将被添加入路由表中。
通向 ISP1 的链路激活后即会发生此情况。
如果通向 ISP1 的链路发生故障，第一条默认路由就会被装入路由表中。
只有在管理员使用no ip route 0.0.0.0 0.0.0.0 172.16.1.1命令手动禁用第二条默认路由后，第一条默认路由才能被装入路由表中。