单选题PCM编码是把模拟信号数字化的过程，通常模拟话音信道的带宽是4000Hz，则在数字化时采样频率至少为______次/秒。

单选题某公司拥有一个C类地址块212.253.115.0/24，网络拓扑结构如下图所示。在主机PCI的DOS命令窗口中，运行arp-a命令显示PCI的ARP缓存，得到结果如下图所示。若采用抓包工具在交换机中捕获的、由PCI以太接口发出的某个数据帧的源地址为10:0e:3c:95:64:e5，目的地址为0d:4f:35:23:5d:8a，则PCI所配置的IP地址和子网掩码分别是______；路由器eth0网卡所配置的IP地址是______。

单选题Linux操作系统中，网络管理员可能通过修改（ ）文件对 Web服务器端口进行配置。

单选题按照802.1d生成树协议（STP），在交换机互联的局域网中， （61） 的交换机被选为根交换机。

单选题某公司网络的地址是 200.16.192.0/18，划分成 16个子网，下面的选项中，不属于这 16个子网地址的是（ ）

单选题美国A公司与中国B企业进行技术合作，合同约定使用一项获得批准并在有效期内的中国专利，但该项技术未在其他国家和地区申请专利，依照该专利生产的产品在 (8) 销售，美国A公司需要向中国B企业支付这项中国专利的许可使用费。

单选题下图所示的网络拓扑中配置了 RIP 协议，且 RIP 协议已更新完成

单选题在VOIP 系统中，通过__（ ）__对声音信号进行压缩编码。

单选题 (66) is used to ensure the confidentiality, integrity and authenticity of the two end points in the private network. (67) , an application-layer protocol, authenticates each peer in an IPsec transaction. IKE negotiates security policy, determining which algorithm may be used to set up the tunnel. It also handles the exchange of session keys used for that one transaction. Networks that use (68) to secure data traffic can automatically authenticate devices by using (69) , which verify the identities of the two users who are sending information back and forth. IPsec can be ideal way to secure data in large networks that require secure connections among many devices. Users deploying IPsec can (70) their network infrastructure without affecting the applications on individual computer. The protocol suite is available as a software-only upgrade to the network infrastructure. This alows security to be implemented without costly changes to each computer. Most important, IPsec allows interoperability among different network devices, PCs and other computing systems.

单选题关于虚拟专用网，下面正确的语句是 （ ） 。

单选题Most IP layer-based proxy mechanisms, such as network address translation (NAT), only support uni-directional proxy, from the internal network to external network (the Internet). The proxy establishes the communication channel by (66) IP addresses. The IP addresses must be (67) . These proxy mechanisms prevent applications that must establish return data channels from establishing their data channels, such as, multimedia applications. IP layer-based proxy mechanisms need additional software (68) for each application that uses (69) channels. SOCKS identifies communication targets through domain names, overcoming the restriction of using private IP addresses. SOCKS can use domain names to establish communication between separate LANs, with (70) IP addresses.

单选题一名攻击者向一台远程主机发送特定的数据包，但是不想远程主机响应这个数据包。它采用的攻击手段可能是 (63) 。

单选题按照网络分级设计模型，通常把网络设计为3 层，即核心层、汇聚层和接入层，以下关于分级网络的描述中，不正确的是 （ ） 。

单选题活动目录(Active Directory)是由组织单元、域、 (39) 和域林构成的层次结构，安装活动目录要求分区的文件系统为 (40) 。

单选题Routing protocols use different techniques for assigning (71) to individual networks. Further, each routing protocol forms a metric aggregation in a different way. Most routing protocols can use multiple paths if the paths have an equal (72) Some routing protocols can even use multiple paths when paths have an unequal cost. In either case, load (73) can improve overall allocation of network bandwidth. When multiple paths are used, there are several ways to distribute the packets. The two most common mechanisms are per-packet load balancing and per-destination load balancing. Per-packet load balancing distributes the (74) across the possible routes in a manner proportional to the route metrics. Per-destination load balancing distributes packets across the possible routes based on (75)

单选题以下对几种网络管理工具/命令的描述中，错误的是______。 A．常见的网络数据监听工具有Sniffer Pro、Iris、TCPdump、Wireshark等 B．常用的漏洞扫描工具有ISS、MBSA、WSUS、X-Scanner等 C．tracert可以发现数据包到达目标主机所经过的路由器和到达时间 D．sniffer软件能够使网络接口处于杂收模式，从而可截获网络上传输的分组

单选题设信道带宽为3400Hz，采用PCM编码，采样周期为125μs，每个样本量化为256个等级，则信道的数据速率为______。

单选题一个主机的IP地址是172．16．2．12/24，该主机所属的网络地址是______。 A．172.0.0.0 B．172.16.0.0 C．172.16.2.0 D．172.16.1.0