思科认证考试 CCNA

思科认证考试 CCNA 1 Which three factors should be considered when implementing a Layer 2 protocol in a network? (Choose three.) the Layer 3 protocol selected the geographic scope of the network the PDU(数据单元) defined by the transport layer the physical layer implementation the number of hosts to be interconnected 2 Refer to the exhibit. Assuming that the network in the exhibit is converged(收敛) meaning the routing tables and ARP tables are complete, which MAC address will Host A place in the destination address field of Ethernet frames destined for www.server? 00-1c-41-ab-c0-00 00-0c-85-cf-65-c0 00-0c-85-cf-65-c1 00-12-3f-32-05-af 3 Which options are properties of contention-based media(竞争介质) access for a shared media? (Choose three.) non-deterministic less overhead(开销) one station transmits at a time collisions exist (存在冲突) devices must wait their turn Token(令牌) passing 4 What is true concerning physical and logical topologies? The logical topology is always the same as the physical topology. Physical topologies are concerned with how a network transfers frames. Physical signal paths are defined by Data Link layer protocols. Logical topologies consist(由构成) of virtual connections between nodes. 5 What determines the method of media access control? (Choose two.) network layer addressing media sharing application processes logical topology intermediary device function (中间设备的功能) 6 What is true regarding(关于) media access control? (Choose three.) Ethernet utilizes CSMA/CD (载波侦听 冲突检测) defined as placement of data frames on the media contention-based access is also known as deterministic 802.11 utilizes(利用) CSMA/CD Data Link layer protocols define the rules for access to different media controlled access(受控访问) contains data collisions 7 Which statements describe the logical token-passing topology? (Choose two.) Network usage is on a first come, first serve basis(基础). Computers are allowed to transmit(发送) data only when they possess a token. Data from a host is received by all other hosts.从一台主机发送的数据将被所有的 主机接受 Electronic tokens(电子令牌) are passed sequentially(循序) to each other. Token passing networks have problems with high collision rates. 8 A network administrator has been asked to provide a graphic representation of exactly where the company network wiring and equipment are located in the building. What is this type of drawing? logical topology physical topology cable path wiring grid access topology 9 What is the purpose of the preamble(报头 前导码) in an Ethernet frame? is used as a padding for data is used for timing synchronization(时间同步) is used to identify the source address is used to identify the destination address 10 What statements are true regarding addresses found at each layer of the OSI model? (Choose two.) Layer 2 may identify devices by a physical address burned into the network card Layer 2 identifies the applications that are communicating Layer 3 represents a hierarchical(分层) addressing scheme (编址) Layer 4 directs communication to the proper destination network Layer 4 addresses are used by intermediary devices to forward data (第四层地址 用来转发数据的) 11 Refer to the exhibit. Which statement describes the media access control methods that are used by the networks in the exhibit? All three networks use CSMA/CA None of the networks require media access control. Network 1 uses CSMA/CD(带有冲突检测的载波侦听多路存取) and Network 3 uses CSMA/CA(载波监听多路访问/冲突防止). Network 1 uses CSMA/CA and Network 2 uses CSMA/CD. Network 2 uses CSMA/CA and Network 3 uses CSMA/CD. 12 Refer to the exhibit. How many CRC calculations will take place as traffic routes from the PC to the laptop? 1 2 4 6 8 16 13 Refer to the exhibit. A frame is being sent from the PC to the laptop. Which source MAC and IP addresses will be included in the frame as it leaves RouterB? (Choose two.) source MAC - PC source MAC - S0/0 on RouterA source MAC - Fa0/1 on RouterB source IP - PC source IP - S0/0 on RouterA source IP - Fa0/1 of RouterB 14 Which sublayer of the data link layer prepares a signal to be transmitted at the physical layer? LLC MAC HDLC NIC 15 What two facts are true when a device is moved from one network or subnet to another? (Choose two.) The Layer 2 address must be reassigned. The default gateway address should not be changed. The device will still operate at the same Layer 2 address. Applications and services will need additional port numbers assigned. The Layer 3 address must be reassigned to allow communications to the new network. 16 What is a function of the data link layer? provides the formatting of data provides end-to-end delivery of data between hosts provides delivery of data between two applications provides for the exchange data over a common local media 17 What is a characteristic of a logical point-to-point topology? 点对点拓扑协议 The nodes are physically connected. The physical arrangement of the nodes is restricted. The media access control protocol can be very simple. The data link layer protocol used over the link requires a large frame header. 18 What is a primary purpose(主要目的)capsulating packets into frames? provide routes across the internetwork format the data for presentation to the user Facilitate(有助于)ntry and exit of data on media identify the services to which transported data is associated 19 What is the primary purpose of the trailer in a data link layer frame? define the logical topology provide media access control support frame error detection carry routing information for the frame 20 What are three characteristics of valid Ethernet Layer 2 addresses? (Choose three.) They are 48 binary bits in length. They are considered physical addresses. 16进制) 它们通常有16 They are generally represented in hexadecimal format.( 进制来表示 They consist of four eight-bit octets of binary numbers. They are used to determine the data path through the network. They must be changed when an Ethernet device is added or moved within the network.