最新ccna2答案第五章汇总

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CCNA-Exploration-网络基础知识-第五章练习及答案

17．请参见图示。网络管理员正在排除连接故障，需要确定用于向网络外转发网络数据包的地址。管理员使用netstat -r命令确定该地址时，会发现所有主机将发往外部网络的数据包发送到以下哪个地址？
○10.10.10.26○127.0.0.1○10.10.10.6○10.10.10.1○224.0.0.0
□R1使用192.168.0.1作为下一跳地址将数据包从192.168.12.0网络路由到172.16.0.0网络。
□R3使用172.16.0.1作为下一跳地址将数据包从10.0.0.0网络路由到172.16.0.0网络。
□R2使用192.168.0.1作为下一跳地址将数据包从172.16.0.0网络路由到192.168.12.0网络。
15．请参见图示。图中显示的所有设备均为出厂默认设置。图示拓扑代表多少个广播域？
○3○4○5○7○8○11Otion 216．下列关于路由及其用途的陈述，哪三项是正确的？（选择三项）
□如果找不到通往目的网络的路由，则将数据包返回前一个路由器。
□如果目的网络直接连接的网络，路由器会将数据包转发到目的主机。
○路由器发送ARP请求以确定所需的下一跳地址。
○路由器丢弃数据包。
○路由器将数据包转发到ARP表所示的下一跳。
○路由器将数据包转发到源地址所示的接口。
○路由器将数据包从默认路由条目所确定的接口发出。
Option 2 and Option 5 are correct.
11．将主机分组到同一个网络时应考虑哪些关键因素？（选择三项）
□网关□用途□物理编址□软件版本□地理位置□所有权
Option 2, Option 5, and Option 6 are correct.
12．以下哪一项是路由表条目的组成部分？

（完整版）计算机网络（第二版）胡亮等编著第五章习题及答案

（完整版）计算机⽹络（第⼆版）胡亮等编著第五章习题及答案复习指南：本章共有5.1-5.7七节内容，没有在考试之外的。

5.1-5.2，⽤时25min。

5.3-5.4，⽤时90min。

5.5，⽤时30min。

5.6，⽤时60min。

5.7，⽤时35min。

参考上课⽤时，可推测重点章节为5.3，5.4，5.6。

推荐看PPT。

5.5，5.7掌握概念。

5.1，5.2简单了解。

课后习题：5.1 通讯⼦⽹的最⾼层是哪⼀层？5.2 ⽹络层的两个主要功能是什么？5.3 在OSI模型中，⽹络层提供了哪两种服务？5.4 ⾯向连接的⽹络服务完成⼀次传输需要哪⼏个过程？5.5 说明⾯向连接的服务和⾯向⽆连接的服务的优缺点。

5.6 说明为什么在⽹络中各个结点对虚电路进⾏独⽴编号。

5.7 第三层交换机与传统的路由器相⽐有哪些优点？5.8 路由选择的最基本要求是什么？5.9 什么是⾮适应性路由选择？什么是适应性路由选择？5.10 什么是拥塞？拥塞产⽣的原因是什么？拥塞对系统有什么影响？5.11 拥塞控制的⽅法有哪些？5.12 在流量控制中，如果采⽤数据报⽅式⼯作，容易产⽣什么样的死锁？如果采⽤虚电路的⽅式⼯作，容易产⽣什么样的死锁？5.13 常⽤的计算最短路径的⽅法有哪两种？5.14 ⽐较距离向量路由和链状状态路由？OSPF属于哪类路由协议？BGP协议属于哪类协议？习题参考答案：5.1 通讯⼦⽹的最⾼层是哪⼀层？⽹络层是通讯⼦⽹的最⾼层，也是主机和通讯⼦⽹的接⼝。

5.2 ⽹络层的两个主要功能是什么？交换和路由。

交换是在两个或者多个设备之间建⽴临时链接，使没有物理链路直接相连的两个或者多个设备之间能够通信。

路由是选择从⼀点到另⼀点发送数据包的最佳路径。

5.3 在OSI模型中，⽹络层提供了哪两种服务？OSI: ⾯向连接的⽹络服务（CONS）和⾯向⽆连接的⽹络服务（CLNS）。

TCP/IP: ⾯向⽆连接的⽹络服务（CLNS）。

5.4 ⾯向连接的⽹络服务完成⼀次传输需要哪⼏个过程？发送者发送⼀个连接请求包，接收者使⽤⼀个连接确认包进⾏确认，发送者传输数据，发送者发送⼀个连接终⽌请求包，接收者使⽤⼀个连接终⽌包进⾏确认。

ccna第五章考试题

1对网络电缆采用的连接器不正确可能产生什么后果？会将数据转发到错误的节点。

通过该电缆传输的数据可能发生信号丢失。

将对该电缆中传输的数据采用不正确的信号方法。

该电缆中发送的数据所采用的编码方法将更改，用于补偿不当连接。

2大多数企业LAN 中的双绞线网络电缆使用哪种连接器？BNCRJ-11RJ-45F 型3在网络中传输数据时，物理层的主要作用是什么？创建信号以表示介质上每个帧中的比特为设备提供物理编址确定数据包的网络通路控制数据对介质的访问4数据传输的三种量度标准是什么？（选择三项）实际吞吐量频率幅度吞吐量串扰带宽5UTP 电缆的哪个特征有助于减少干扰的影响？屏蔽层中的金属编织包裹核心的反射涂层电缆中的线对绕绞外皮中的绝缘材料6XYZ 公司正在其数据网络中安装新的电缆。

下列哪两种类型是新架设时最常用的电缆？（选择两项）同轴4 类UTP5 类UTP6 类UTPSTP7使用什么设备可以检查安装的光纤是否存在错误并检查其完整性和介质性能？光注入器OTDRTDR万用表8以下哪项是单模光缆的特征？一般使用LED 作为光源因为有多条光通路，核心相对较粗价格比多模低一般使用激光作为光源9请参见图示。

哪种 5 类电缆用于在主机 A 和主机 B 之间建立以太网连接？同轴电缆全反电缆交叉电缆直通电缆10以下哪项被视为选择无线介质的优点？主机移动更方便安全风险更低减少干扰的影响环境对有效覆盖面积的影响更小11如果在网络中使用非屏蔽双绞线铜缆，导致线对内串扰的原因是什么？相邻线对周围的磁场使用编织线屏蔽相邻线对从电缆远端反射回来的电波因两个节点尝试同时使用介质而导致的冲突12哪种光纤连接器支持全双工以太网？13哪种电缆通常与光缆相关联？主干电缆水平电缆跳线电缆工作区域电缆14在可能存在电气危险或电磁干扰的LAN 安装中，主干布线建议使用哪种类型的介质？同轴光纤5e 类UTP6 类UTP15网络中什么时候使用直通电缆？通过控制台端口连接路由器时连接两台交换机时连接主机与交换机时连接两台路由器时16以下哪些特征描述的是光缆？（选择两项）不受 EMI 或RF I 影响。

CCNA第一学期第五章答案

C C N A第一学期第五章答案集团文件版本号：（M928-T898-M248-WU2669-I2896-DQ586-M1988）最新CCNA第一学期第五章答案一个 MAC 地址包含 6 个字节。

前 3 个字节用于供应商标识，最后 3 个字节必须在同一 OUI 中分配唯一的值。

MAC 地址在硬件中实施。

网卡需要使用 MAC 地址来通过 LAN 通信。

IEEE 规范了 MAC 地址。

争用方法具有不确定性，没有受控访问方法中遇到的开销。

因为设备不需要轮流访问介质，所以无需跟踪次序。

争用方法在介质使用率高的情况下无法很好地扩展。

逻辑链路控制在软件中实施，能够让数据链路层与协议簇的上层协议通信。

网卡驱动程序软件直接与网卡上的硬件交互，可在 MAC 子层和物理介质之间传输数据。

逻辑链路控制在 IEEE 802.2 标准中指定。

IEEE 802.3 是定义不同以太网类型的一组标准。

MAC（介质访问控制）子层负责定位和检索介质上和介质外的帧。

组播 MAC 地址是一个特殊的十六进制数值，以 01-00-5E 开头。

然后将IP 组播组地址的低 23 位换算成以太网地址中剩余的 6 个十六进制字符，作为组播 MAC 地址的结尾。

MAC 地址的剩余位始终为“0”。

在此例中：224（十进制）=> 01-00-5E34（十进制）= 00100010（二进制）= 22（十六进制）56（十进制）= 00111000（二进制）= 38（十六进制）综合结果：01:00:5E:0B:22:38如果整个路径都基于以太网，则目的和源 MAC 地址将随着每个路由器跳数发生变化。

除非网络地址转换处于活动状态，否则目的 IP 地址在整个路径中保持不变。

请参见图示。

由于 PC1 需要向 PC2 发送数据包，因此 PC1 发出一个ARP 请求。

在这种情况下，接下来将发生什么？当一台网络设备要与相同网络中的另一台设备通信时，它会发送广播ARP 请求。

CCNA第一学期各章习题及答案

诶了我累了目录第二章网络通信P2-8第三章应用层功能及协议P9-14第四章OSI传输层P15-20第五章OSI网络层P21-27第六章网络编址-IPv4 P28-34第七章数据链路层P35-40第八章OSI物理层P41-45第九章以太网P46-51第十章网络规划和布线P52-61第十一章配置和测试网络P62-70第一学期末考试P71-91文档末尾返回目录第二章网络通信001 TCP/IP 网络接入层有何作用？路径确定和数据包交换数据表示、编码和控制可靠性、流量控制和错误检测详细规定构成物理链路的组件及其接入方法将数据段划分为数据包002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）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003下列哪三项陈述是对局域网 (LAN) 最准确的描述？（选择三项）LAN 通常位于一个地域内。

此类网络由由一个组织管理。

LAN 中的不同网段之间一般通过租用连接的方式连接。

此类网络的安全和访问控制由服务提供商控制。

LAN 为同一个组织内的用户提供网络服务和应用程序访问。

此类网络的每个终端通常都连接到电信服务提供商 (TSP)。

004 什么是 PDU？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005 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）网络层传输层物理层数据链路层会话层006请参见图示。

所示网络属于哪一类型？WANMANLANWLAN007 以下哪种特征正确代表了网络中的终端设备？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008 第 4 层端口指定的主要作用是什么？标识本地介质中的设备标识源设备和目的设备之间的跳数向中间设备标识通过该网络的最佳路径标识正在通信的源终端设备和目的终端设备标识终端设备内正在通信的进程或服务009 请参见图示。

CCNA 2 Practice Final v5 answers 2013

CCNA 2 Practice Final v5 answers 20131What is the order of packet types used by an OSPF router to establish convergence? Hello, DBD, LSR, LSU, LSAckLSAck, Hello, DBD, LSU, LSRLSU, LSAck, Hello, DBD, LSRHello, LSAck, LSU, LSR, DBD2Which two keywords can be used in an access control list to replace a wildcard mask or address and wildcard mask pair? (Choose two.)mostallgthostanysome3Which network design may be recommended for a small campus site that consists of a single building with a few users?a collapsed core network designa network design where the access and core layers are collapsed into a single layera three-tier campus network design where the access, distribution, and core are all separate layers, each one with very specific functionsa network design where the access and distribution layers are collapsed into a single layer 4Refer to the exhibit. A network administrator is configuring inter-VLAN routing on a network. For now, only one VLAN is being used, but more will be added soon. What is the missing parameter that is shown as the highlighted question mark in the graphic?It identifies the subinterface.It identifies the native VLAN number.It identifies the number of hosts that are allowed on the interface.It identifies the VLAN number.It identifies the type of encapsulation that is used.5A router with two LAN interfaces, two WAN interfaces, and one configured loopback interface is operating with OSPF as its routing protocol. What does the router OSPF process use to assign the router ID?the IP address of the interface that is configured with priority 0the highest IP address on the LAN interfacesthe OSPF area ID that is configured on the interface with the highest IP addressthe highest IP address that is configured on the WAN interfacesthe loopback interface IP addressRefer to the exhibit. A PC at address 10.1.1.45 is unable to access the Internet. What is the most likely cause of the problem?The NAT pool has been exhausted.The inside and outside interfaces have been configured backwards.The wrong netmask was used on the NAT pool.Access-list 1 has not been configured properly.7Which DHCP IPv4 message contains the following information?Destination address: 255.255.255.255Client IPv4 address: 0.0.0.0Default gateway address: 0.0.0.0Subnet mask: 0.0.0.0DHCPOFFERDHCPREQUESTDHCPACKDHCPDISCOVERRefer to the exhibit. R1 and R2 are OSPFv3 neighbors. Which address would R1 use as the next hop for packets that are destined for the Internet?2001:DB8:C5C0:1::22001:DB8:ACAD:1::2FE80::21E:BEFF:FEF4:5538FF02::59Which command will create a static default route on R1 to send all traffic to the Internet and use serial 0/0 as the exit interface?R1(config)# ip route 0.0.0.0 255.255.255.0 serial 0/0R1(config)# ip route 255.255.255.255 0.0.0.0 serial 0/0R1(config)# ip route 0.0.0.0 0.0.0.0 serial 0/0R1(config)# ip route 0.0.0.0 255.255.255.255 serial 0/010A client is using SLAAC to obtain an IPv6 address for its interface. After an address has been generated and applied to the interface, what must the client do before it can begin to use this IPv6 address?It must send an ICMPv6 Neighbor Solicitation message to ensure that the address is not already in use on the network.It must send a DHCPv6 INFORMATION-REQUEST message to request the address ofthe DNS server.It must send an ICMPv6 Router Solicitation message to determine what default gateway it should use.It must send a DHCPv6 REQUEST message to the DHCPv6 server to request permission to use this address.11What is the effect of the access control list wildcard mask 0.0.0.15? (Choose two.)The first 32 bits of a supplied IP address will be matched.The first 28 bits of a supplied IP address will be ignored.The last four bits of a supplied IP address will be ignored.The last four bits of a supplied IP address will be matched.The last five bits of a supplied IP address will be ignored.The first 28 bits of a supplied IP address will be matched.12How will a router handle static routing differently if Cisco Express Forwarding is disabled?It will not perform recursive lookups.Static routes that use an exit interface will be unnecessary.Serial point-to-point interfaces will require fully specified static routes to avoid routing inconsistencies.Ethernet multiaccess interfaces will require fully specified static routes to avoid routing inconsistencies.13Fill in the blank.Using router-on-a-stick inter-VLAN routing, how many subinterfaces have to be configured to support 10 VLANs?1014Refer to the exhibit. The student on the H1 computer continues to launch an extended ping with expanded packets at the student on the H2 computer. The school network administrator wants to stop this behavior, but still allow both students access toweb-based computer assignments. What would be the best plan for the network administrator?Apply an outbound standard ACL on R2 S0/0/1.Apply an inbound standard ACL on R1 Gi0/0.Apply an outbound extended ACL on R1 S0/0/1.Apply an inbound extended ACL on R1 Gi0/0.Apply an inbound extended ACL on R2 Gi0/1.15What is an advantage of using dynamic routing protocols instead of static routing?fewer router resource overhead requirementsability to actively search for new routes if the current path becomes unavailable more secure in controlling routing updateseasier to implement16A network administrator is testing IPv6 connectivity to a web server. The network administrator does not want any other host to connect to the web server except for the one test computer. Which type of IPv6 ACL could be used for this situation?an extended, named, or numbered ACLonly a named ACLonly an extended ACLonly a standard ACLa standard or extended ACL17Refer to the exhibit. Host A has sent a packet to host B. What will be the source MAC and IP addresses on the packet when it arrives at host B?Source MAC: 00E0.FE91.7799Source IP: 192.168.1.1Source MAC: 00E0.FE10.17A3Source IP: 192.168.1.1Source MAC: 00E0.FE91.7799Source IP: 10.1.1.1Source MAC: 00E0.FE10.17A3Source IP: 10.1.1.10Source MAC: 00E0.FE91.7799Source IP: 10.1.1.1018How many classful networks are summarized by the static summary route ip route192.168.32.0 255.255.248.0 S0/0/0?4281619.A small company has a web server in the office that is accessible from the Internet. The IP address 192.168.10.15 is assigned to the web server. The network administrator is configuring the router so that external clients can access the web server over the Internet. Which item is required in the NAT configuration?an ACL to identify the local IPv4 address of the web serverthe ip nat inside source command to link the inside local and inside global addressesthe keyword overload for the ip nat inside source commandan IPv4 address pool20What is a result of connecting two or more switches together?The number of collision domains is reduced.The size of the broadcast domain is increased.The number of broadcast domains is increased.The size of the collision domain is increased.21Refer to the exhibit. If the IP addresses of the default gateway router and the DNS server are correct, what is the configuration problem?The DNS server and the default gateway router should be in the same subnet.The default-router and dns-server commands need to be configured with subnet masks. The IP address of the DNS server is not contained in the excluded address list.The IP address of the default gateway router is not contained in the excluded address list.22When routing a large number of VLANs, what are two disadvantages of using therouter-on-a-stick inter-VLAN routing method rather than the multilayer switch inter-VLAN routing method? (Choose two.)Multiple SVIs are needed.Multiple subinterfaces may impact the traffic flow speed.Router-on-a-stick requires subinterfaces to be configured on the same subnets.Router-on-a-stick requires multiple physical interfaces on a router.A dedicated router is required.23How is the router ID for an OSPFv3 router determined?the highest EUI-64 ID on an active interfacethe highest IPv4 address on an active interfacethe highest IPv6 address on an active interfacethe lowest MAC address on an active interface24What does an OSPF area contain?routers whose SPF trees are identicalrouters that have the same link-state information in their LSDBsrouters that share the same router IDrouters that share the same process ID25Which command will verify the status of both the physical and the virtual interfaces on a switch?show ip interface briefshow running-configshow vlanshow startup-config26Which switching method provides error-free data transmission?fast-forwardintegrity-checkingstore-and-forwardfragment-free27What is associated with link-state routing protocols?split horizonshortest-path first calculationslow processor overheadrouting loopspoison reverse28Refer to the exhibit. Which would be chosen as the router ID of R2? 2001:DB8:CAFE:A001::/642001:DB8:CAFE:2::/64The router ID has to be manually configured.LLA: FE80::229Place the options in the following order: Step 3– target left blank –Step 4Step 2Step 130Refer to the exhibit. A network administrator is investigating a lag in network performance and issues the show interfaces fastethernet 0/0 command. Based on the output that is displayed, what two items should the administrator check next? (Choose two.)duplex settingscable lengthselectrical interferenceincorrect cable typesdamaged cable termination31The PT initialization was skipped. You will not be able to view the PT activity.Open the PT activity. Perform the tasks in the activity instructions and then answer the question.To verify that the SVI is configured correctly, answer this question: Which ping command completed successfully?ping 192.168.25.7ping 192.168.25.10ping 192.168.25.9ping 192.168.25.832An administrator created and applied an outbound Telnet extended ACL on a router to prevent router-initiated Telnet sessions. What is a consequence of this configuration?The ACL will work as desired as long as it is applied to the correct interface.The ACL will not work as desired because an outbound ACL cannot blockrouter-initiated traffic.The ACL will work as long as it will be applied to all vty lines.The ACL will not work because only standard ACLs can be applied to vty lines.33What is the effect of entering the network 192.168.10.1 0.0.0.0 area 0 command in router configuration mode?OSPF advertisements will include the specific IPv4 address 192.168.10.1.OSPF advertisements will include the network on the interface with the IPv4 address 192.168.10.1.This command will have no effect because it uses a quad zero wildcard mask.The interface with the IPv4 address 192.168.10.1 will be a passive interface.34Which type of static route typically uses the distance parameter in the ip route global configuration command?standard static routefloating static routedefault static routesummary static route35Which command would be best to use on an unused switch port if a company adheres to the best practices as recommended by Cisco?ip dhcp snoopingswitchport port-security mac-address stickyshutdownswitchport port-security violation shutdownswitchport port-security mac-address sticky mac-address36What is a disadvantage when both sides of a communication use PAT?The flexibility of connections to the Internet is reduced.Host IPv4 addressing is complicated.The security of the communication is negatively impacted.End-to-end IPv4 traceability is lost.37What is meant by the term “best match” when applied to the routing table lookup process?network matchsupernet matchexact matchlongest match38Place the options in the following order:hierarchicalmodularityresiliency– not scored –flexibility39Fill in the blank. Do not use abbreviations.The duplex full command configures a switch port to operate in the full-duplex mode. 40An administrator is trying to remove configurations from a switch. After using the command erase startup-config and reloading the switch, the administrator finds that VLANs 10 and 100 still exist on the switch. Why were these VLANs not removed?These VLANs are default VLANs that cannot be removed.Because these VLANs are stored in a file that is called vlan.dat that is located in flash memory, this file must be manually deleted.These VLANs can only be removed from the switch by using the no vlan 10 and no vlan 100 commands.These VLANs cannot be deleted unless the switch is in VTP client mode.41An administrator attempts to change the router ID on a router that is running OSPFv3 by changing the IPv4 address on the router loopback interface. Once the IPv4 address is changed, the administrator notes that the router ID did not change. What two actions can the administrator take so that the router will use the new IPv4 address as the router ID? (Choose two.)Copy the running configuration to NVRAM.Reboot the router.Disable and re-enable IPv4 routing.Shut down and re-enable the loopback interface.Clear the IPv6 OSPF process.42Refer to the exhibit. In the routing table entry, what is the administrative distance?2412212043Which two pieces of information are required when creating a standard access control list? (Choose two.)subnet mask and wildcard maskaccess list number between 100 and 199access list number between 1 and 99destination address and wildcard masksource address and wildcard mask44Refer to the exhibit. Inter-VLAN communication between VLAN 10, VLAN 20, and VLAN 30 is not successful. What is the problem?The access interfaces do not have IP addresses and each should be configured with an IP address.The switch interface FastEthernet0/1 is configured as an access interface and should be configured as a trunk interface.The switch interfaces FastEthernet0/2, FastEthernet0/3, and FastEthernet0/4 are configured to not negotiate and should be configured to negotiate.The switch interface FastEthernet0/1 is configured to not negotiate and should be configured to negotiate.45In a routing table which route can never be an ultimate route?parent routechild routelevel two routelevel one route46In which type of attack does a malicious node request all available IP addresses in the address pool of a DHCP server in order to prevent legitimate hosts from obtaining network access?DHCP snoopingMAC address floodingCAM table overflowDHCP starvation47Refer to the exhibit. What address will be used as the router ID for the OSPFv3 process?10.1.1.12001:DB8:ACAD:1::12001:DB8:CAFE:1::1192.168.1.11.1.1.148Refer to the exhibit. An administrator is trying to configure PAT on R1, but PC-A is unable to access the Internet. The administrator tries to ping a server on the Internet from PC-A and collects the debugs that are shown in the exhibit. Based on this output, what is most likely the cause of the problem?The NAT source access list matches the wrong address range.The inside and outside NAT interfaces have been configured backwards.The inside global address is not on the same subnet as the ISP.The address on Fa0/0 should be 64.100.0.1.49A college student is studying for the Cisco CCENT certification and is visualizing extended access lists. Which three keywords could immediately follow the keywords permit or deny as part of an extended access list? (Choose three.)wwwudptcpicmpftptelnet50When does a switch use frame filtering?The destination MAC address is for a host on a different network segment from the source of the traffic.The destination MAC address is for a host with no entry in the MAC address table.The destination MAC address is for a host on a network supported by a different router.The destination MAC address is for a host on the same network segment as the source of the traffic.。

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答案第五章

第五章 RIPv1 CCNA2 Exploration: 路由协议和概念 (2010-12-15 18:07:13) 转载▼标签：杂谈分类： 2010｜CCNA2官方试题--路由 1窗体顶端ERouting Chapter 7 - CCNA Exploration: 路由协议和概念 (版本 4.0)以下行显示在 show ip route 命令的输出中。

R 192.168.3.0/24 [120/3] via 192.168.2.2, 00:00:30, Serial0/0该路由度量的值是什么？3122030120 窗体底端2窗体顶端下列关于 RIPv1 特性的陈述中，哪两项是正确的？（选择两项。

）它是一种距离矢量路由协议。

它会在路由更新中通告路由的地址和子网掩码。

RIP 消息的数据部分封装在 TCP 数据段中。

RIP 消息的数据部分封装在 UDP 数据段中。

它每 15 秒广播一次更新。

它最多允许路由域中存在 15 台路由器。

窗体底端3窗体顶端请参见图示。

图中所示的网络运行RIPv1。

不久前其中添加了192.168.10.0/24 网络，该网络将只包含最终要防止向新网络中的最终用户设备发送RIPv1 更新，同时允许将此新网络通告给其它路由器，应该在Rou 什么命令？Router1(config-router)# no router ripRouter1(config-router)# network 192.168.10.0Router1(config-router)# no network 192.168.10.0Router1(config-router)# passive-interface fastethernet 0/0Router1(config-router)# passive-interface serial 0/0/0窗体底端4 窗体顶端请参见图示。

该网络包含多台路由器。

ccna第二学期练习答案中文

ERouting Chapter 1 - CCNA Exploration: 路由协议和概念(版本4.0)1口令可用于限制对Cisco IOS 所有或部分内容的访问。

请选择可以用口令保护的模式和接口。

（选择三项。

）VTY 接口控制台接口特权执行模式2路由器从相连的以太网接口收到消息后，会更改哪项报头地址，再将消息从另一个接口发送出去？第 2 层源地址和目的地址3请参见图示。

网络管理员已经为路由器连接到直连网络的接口配置了如图所示的IP 地址。

从路由器ping 相连网络上的主机口之间相互ping 都会遭到失败。

此问题最可能的原因是什么？必须使用no shutdown命令启用接口。

4请参见图示。

主机 A ping 主机B。

当R4 收到对以太网接口的ping 时，哪两块报头信息包括在内？（选择两项。

）目的IP 地址：192.168.10.134目的MAC 地址：9999.DADC.12345网络管理员刚把新配置输入Router1。

要将配置更改保存到NVRAM，应该执行哪一条命令？Router1# copy running-config startup-config6您需要配置图中所示的串行连接，必须在Sydney 路由器上发出以下哪条配置命令才能与Melbourne 站点建立连接？（选Sydney(config-if)# ip address 201.100.53.2 255.255.255.0Sydney(config-if)# no shutdownSydney(config-if)# clock rate 560007请参见图示。

从路由器的运行配置输出可得出什么结论？显示的命令决定了路由器的当前运行情况。

8请参见图示。

在主机 2 连接到LAN 上的交换机后，主机2 无法与主机 1 通信。

导致此问题的原因是什么？主机 1 和主机2 位于不同的网络中。

9输入以下命令的作用是什么？R1(config)# line vty 0 4R1(config-line)# password check123R1(config-line)# login设置通过Telnet 连接该路由器时使用的口令10以下哪一项正确描述了路由器启动时的顺序？加载bootstrap、加载IOS、应用配置11加载配置文件时的默认顺序是怎样的？NVRAM、TFTP、CONSOLE12请参见图示。

《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。

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。

CCNA 2 Chapter 5 Exam Answer

CCNA 2 Chapter 5Exam Answer1. Refer to the exhibit. The switch does the routing for the hosts that connect to VLAN 5. If the PC accesses a web server from the Internet, at what point will a VLAN number be added to the frame?CCNA 2 Chapter 5 Exam Answer 001 (v5.02, 2015)∙point A∙point B∙point C∙point D∙point E∙No VLAN number is added to the frame in this design.2. Which type of inter-VLAN communication design requires the configuration of multiple subinterfaces?∙router on a stick∙routing via a multilayer switch∙routing for the management VLAN∙legacy inter-VLAN routing3. What is a disadvantage of using router-on-a-stick inter-VLAN routing?∙does not support VLAN-tagged packets∙requires the use of more physical interfaces than legacy inter-VLAN routing∙does not scale well beyond 50 VLANs∙requires the use of multiple router interfaces configured to operate as access links4. How is traffic routed between multiple VLANs on a multilayer switch?∙Traffic is routed via physical interfaces.∙Traffic is routed via internal VLAN interfaces.∙Traffic is broadcast out all physical interfaces.∙Traffic is routed via subinterfaces.5. A small college uses VLAN 10 for the classroom network and VLAN 20 for the office network. What is needed to enable communication between these two VLANs while using legacy inter-VLAN routing?∙ A router with at least two LAN interfaces should be used.∙Two groups of switches are needed, each with ports that are configured for one VLAN.∙ A router with one VLAN interface is needed to connect to the SVI on a switch.∙ A switch with a port that is configured as trunk is needed to connect to a router.6. Which statement describes a disadvantage of using router subinterfaces for inter-VLAN routing?∙It is more expensive than using individual router interfaces.∙Routed traffic must contend for bandwidth on a single router interface.∙Trunking cannot be used to connect the router to the switch.∙All untagged traffic is dropped.7. Refer to the exhibit. A network administrator needs to configure router-on-a-stick for the networks that are shown. How many subinterfaces will have to be created on the router if each VLAN that is shown is to be routed and each VLAN has its own subinterface?CCNA 2 Chapter 5 Exam Answer 002 (v5.02, 2015)∙ 1∙ 2∙ 3∙4∙ 58. Refer to the exhibit. A network administrator has configured router CiscoVille with the above commands to provide inter-VLAN routing. What command will be required on a switch that is connected to the Gi0/0 interface on router CiscoVille to allow inter-VLAN routing??CCNA 2 Chapter 5 Exam Answer 003 (v5.02, 2015)∙switchport mode access∙no switchport∙switchport mode trunk∙switchport mode dynamic desirable9. Refer to the exhibit. Router RA receives a packet with a source address of 192.168.1.35 and a destination address of 192.168.1.85. What will the router do with this packet?CCNA 2 Chapter 5 Exam Answer 004 (v5.02, 2015)∙The router will drop the packet.∙The router will forward the packet out interface FastEthernet 0/1.1.∙The router will forward the packet out interface FastEthernet 0/1.2.∙The router will forward the packet out interface FastEthernet 0/1.3.∙The router will forward the packet out interface FastEthernet 0/1.2 and interface FastEthernet 0/1.3.10. Refer to the exhibit. Communication between the VLANs is not occurring. What could be the issue?CCNA 2 Chapter 5 Exam Answer 005 (v5.02, 2015)∙The wrong port on the router has been used.∙The Gi1/1 switch port is not in trunking mode.∙ A duplex issue exists between the switch and the router.∙Default gateways have not been configured for each VLAN.11. Inter-VLAN communication is not occurring in a particular building of a school. Which two commands could the network administrator use to verify that inter-VLAN communication was working properly between a router and a Layer 2 switch when the router-on-a-stick design method is implemented? (Choose two.)∙From the router, issue the show ip route command.∙From the router, issue the show interfaces trunk command.∙From the router, issue the show interfaces interface command.∙From the switch, issue the show vlans command.∙From the switch, issue the show interfaces trunk command.∙From the switch, issue the show interfaces interface command.12. Refer to the exhibit. A network administrator is verifying the configuration of inter-VLAN routing. Users complain that PCs on different VLANs cannot communicate. Based on the output, what are two configuration errors on switch interface Gi1/1? (Choose two.)CCNA 2 Chapter 5 Exam Answer 006 (v5.02, 2015)∙Gi1/1 is in the default VLAN.∙Voice VLAN is not assigned to Gi1/1.∙Gi1/1 is configured as trunk mode.∙Negotiation of trunking is turned on on Gi1/1.∙The trunking encapsulation protocol is configured wrong.13. Refer to the exhibit. A network administrator is verifying the configuration of inter-VLAN routing. Users complain that PC2 cannot communicate with PC1. Based on the output, what is the possible cause of the problem?CCNA 2 Chapter 5 Exam Answer 007 (v5.02, 2015)∙Gi0/0 is not configured as a trunk port.∙The command interface GigabitEthernet0/0.5 was entered incorrectly.∙There is no IP address configured on the interface Gi0/0.∙The no shutdown command is not entered on subinterfaces.∙The encapsulation dot1Q 5 command contains the wrong VLAN.14. Refer to the exhibit. After attempting to enter the configuration that is shown in router RTA, an administrator receives an error and users on VLAN 20 report that they are unable to reach users on VLAN 30. What is causing the problem?CCNA 2 Chapter 5 Exam Answer 008 (v5.02, 2015)∙Dot1q does not support subinterfaces.∙There is no address on Fa0/0 to use as a default gateway.∙RTA is using the same subnet for VLAN 20 and VLAN 30.∙The no shutdown command should have been issued on∙Fa0/0.20 and Fa0/0.30.15. Refer to the exhibit. A router-on-a-stick configuration was implemented for VLANs 15, 30, and 45, according to the show running-config command output. PCs on VLAN 45 that are using the 172.16.45.0 /24 network are having trouble connecting to PCs on VLAN 30 in the 172.16.30.0 /24 network. Which error is most likely causing this problem??CCNA 2 Chapter 5 Exam Answer 009 (v5.02, 2015)∙The wrong VLAN has been configured on GigabitEthernet 0/0.45.∙The command no shutdown is missing on GigabitEthernet 0/0.30.∙The GigabitEthernet 0/0 interface is missing an IP address.∙There is an incorrect IP address configured on GigabitEthernet 0/0.30.16. Refer to the exhibit. A network administrator is configuring RT1 for inter-VLAN routing. The switch is configured correctly and is functional. Host1, Host2, and Host3 cannot communicate with each other. Based on the router configuration, what is causing the problem?CCNA 2 Chapter 5 Exam Answer 010 (v5.02, 2015)∙Interface Fa0/0 is missing IP address configuration information.∙IP addresses on the subinterfaces are incorrectly matched to the VLANs.∙Each subinterface of Fa0/0 needs separate no shutdown commands.∙Routers do not support 802.1Q encapsulation on subinterfaces. 17. What condition is required to enable Layer 3 switching?∙The Layer 3 switch must have IP routing enabled.∙All participating switches must have unique VLAN numbers.∙All routed subnets must be on the same VLAN.∙Inter-VLAN portions of Layer 3 switching must use router-on-a-stick.18. Refer to the exhibit. Which command can the administrator issue to change the VLAN10 status to up??CCNA 2 Chapter 5 Exam Answer 011 (v5.02, 2015)∙Switch1(config)# interface vlan 10Switch1(config-if)# no shutdown?∙Switch1(config)# interface vlan 10Switch1(config-if)# ip address 192.168.10.1 255.255.255.0?∙Switch1(config)# interface vlan 10Switch1(config-if)# ip address 192.168.10.1 255.255.255.0Switch1(config-if)# no shutdown?∙Switch1(config)# vlan 10Switch1(config-vlan)# exit19. While configuring inter-VLAN routing on a multilayer switch, a network administrator issues the no switchport command on an interface that is connected to another switch. What is the purpose of this command?∙to create a routed port for a single network∙to provide a static trunk link∙to create a switched virtual interface∙to provide an access link that tags VLAN traffic20. What is a disadvantage of using multilayer switches for inter-VLAN routing?∙Multilayer switches have higher latency for Layer 3 routing.∙Multilayer switches are more expensive than router-on-a-stick implementations.∙Spanning tree must be disabled in order to implement routing on a multilayer switch.∙Multilayer switches are limited to using trunk links for Layer 3 routing.21. Fill in the blank with an acronym.While configuring inter-VLAN routing on a multilayer switch, a/an svi is used as a virtual-routed VLAN interface.22. Fill in the blank. Do not use abbreviations.A network engineer is troubleshooting the configuration of new VLANs on a network. ?Which command is used to display the list of VLANs that exists on the switch?show vlan23. Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.Fill in the blank. Do not use abbreviations.Which command is missing on the Layer 3 switch to restore the full connectivity between PC1 and the web server?ip address 192.168.20.1 255.255.255.0。

计算机网络第五章课后答案

计算机网络第五章课后答案第五章5—01 试说明运输层在协议栈中的地位和作用，运输层的通信和网络层的通信有什么重要区别？为什么运输层是必不可少的？答：运输层处于面向通信部分的最高层，同时也是用户功能中的最低层，向它上面的应用层提供服务运输层为应用进程之间提供端到端的逻辑通信，但网络层是为主机之间提供逻辑通信（面向主机，承担路由功能，即主机寻址及有效的分组交换）。

各种应用进程之间通信需要“可靠或尽力而为”的两类服务质量，必须由运输层以复用和分用的形式加载到网络层。

5—02 网络层提供数据报或虚电路服务对上面的运输层有何影响？答：网络层提供数据报或虚电路服务不影响上面的运输层的运行机制。

但提供不同的服务质量。

5—03 当应用程序使用面向连接的TCP 和无连接的IP 时，这种传输是面向连接的还是面向无连接的？答：都是。

这要在不同层次来看，在运输层是面向连接的，在网络层则是无连接的。

5—04 试用画图解释运输层的复用。

画图说明许多个运输用户复用到一条运输连接上，而这条运输连接有复用到IP 数据报上。

5—05 试举例说明有些应用程序愿意采用不可靠的UDP，而不用采用可靠的TCP 。

答：VOIP：由于语音信息具有一定的冗余度，人耳对VOIP数据报损失由一定的承受度，但对传输时延的变化较敏感。

有差错的UDP数据报在接收端被直接抛弃，TCP 数据报出错则会引起重传，可能带来较大的时延扰动。

因此VOIP宁可采用不可靠的UDP，而不愿意采用可靠的TCP 。

5—06 接收方收到有差错的UDP用户数据报时应如何处理？答：丢弃5—07 如果应用程序愿意使用UDP来完成可靠的传输，这可能吗？请说明理由答：可能，但应用程序中必须额外提供与TCP 相同的功能。

5—08 为什么说UDP是面向报文的，而TCP 是面向字节流的？答：发送方UDP 对应用程序交下来的报文，在添加首部后就向下交付IP 层。

UDP对应用层交下来的报文，既不合并，也不拆分，而是保留这些报文的边界。

ccna第二学期练习答案

c c n a第二学期练习答案(总45页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--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 相连网络路由器接口之间相互 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 R 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 路由下哪条配置命令才能与 Melbourne 站点建立连接（选择三项）Sydney(config-if)# ip addressSydney(config-if)# no shutdownSydney(config-if)# clock rate 560007请参见图示。

从路由器的运行配置输出可得出什么结论显示的命令决定了路由器的当前运行情况。

8请参见图示。

在主机 2 连接到 LAN 上的交换机后，主主机 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。

计算机网络_第5章习题答案

第五章练习题答案5.1 网络互连有何实际意义？进行网络互连时，有哪些共同的问题需要解决？答：网络互连使得相互连接的网络中的计算机之间可以进行通信，也就是说从功能上和逻辑上看，这些相互连接的计算机网络组成了一个大型的计算机网络。

网络互连可以使处于不同地理位置的计算机进行通信，方便了信息交流，促成了当今的信息世界。

需要解决的问题有：不同的寻址方案；不同的最大分组长度；不同的网络介入机制；不同的超时控制；不同的差错恢复方法；不同的状态报告方法；不同的路由选择技术；不同的用户接入控制；不同的服务（面向连接服务和无连接服务）；不同的管理与控制方式；等等。

注：网络互连使不同结构的网络、不同类型的机器之间互相连通，实现更大范围和更广泛意义上的资源共享。

5.2 转发器、网桥和路由器都有何区别？答：1）转发器、网桥、路由器、和网关所在的层次不同。

转发器是物理层的中继系统。

网桥是数据链路层的中继系统。

路由器是网络层的中继系统。

在网络层以上的中继系统为网关。

2）当中继系统是转发器或网桥时，一般并不称之为网络互连，因为仍然是一个网络。

路由器其实是一台专用计算机，用来在互连网中进行路由选择。

一般讨论的互连网都是指用路由器进行互连的互连网络。

5.3 试简单说明IP、ARP、RARP和ICMP协议的作用。

答：IP：网际协议，TCP/IP 体系中两个最重要的协议之一，IP 使互连起来的许多计算机网络能够进行通信。

无连接的数据报传输. 数据报路由。

ARP（地址解析协议）实现地址转换，将IP地址映射成物理地址。

RARP（逆向地址解析协议）将物理地址映射成IP 地址。

ICMP：Internet 控制消息协议，进行差错控制和传输控制，减少分组的丢失。

注：ICMP 协议帮助主机完成某些网络参数测试，允许主机或路由器报告差错和提供有关异常情况报告，但它没有办法减少分组丢失，这是高层协议应该完成的事情。

IP 协议只是尽最大可能交付，至于交付是否成功，它自己无法控制。

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。