CCNA TK 常见问题及解法集中贴
1. Which statements are true about EIGRP sucessor routes?(Choose two)A. A sucessor route is used by EIGRP to forward traffic to a destination.
B. Sucessor routes are saved in the topology table to be used if the primary route fails.
C. Sucessor routes are flagged as "active" in the routing table.
D. A sucessor route may be backed up by a feasible successor route.
E. Successor routes are stored in the neighbor table following the discovery process.
F. Successors are not used in EIGRP.
Answer: A, D
解法: 这里存在争议的选项是A和B，选项A，继任者路由即主路由，路由表中的路由，用于路由器转发流量到目的网络使用；是正确的。
而B只对了一半，saved in topology正确，而used if the primary route fails错误，Sucessor = primary route。
2. The statements below compare and contrast link stat and distance vector routing protocols.Which of these are true?(Choose two)
A.Distance vector protocols send the entire routing table to directly connected neighbors
B.Distance vector protocols are responsible for sending updates to all networks listed in the routing table.
C. Link state protocols are protocols area responsible for sending the entire routing table to the whole network.
D. Link state protocols send updates regarding their own links status to all other routers on the network.
Answer: A,D
解法: 距离矢量路由协议与链路状态路由协议的比较，距离矢量路由协议将与直连的邻居交换整张路由表，而使用链路状态路由协议将只发送自已的链路状态更新（LSU）给网络内的其他路由器。
3. What are the characteristic of link stat routing protocols?(Choose all that apply).
A.The exchange of advertisement is triggered by a change in the network.
B.All routers exchange routing tables with each other in a multipoint network.
C.Packets are routed based upon the shortest path to the destination.
D.Paths are chosen depending on the cost efficiency factor.
E.Every router in an OSPF area is capable of representing the entire network topology.
F.Only the designated router in an OSPF area can represent the entire network topology.
Answer: A,C,E
解法: 当网络发生变化的时候发送触发式更新。
路径的选择基于最短路径优先算法（SPF）。
一个区域里的每台路由器都保持有该区域中所有路由器或链路的详细信息。
4. Exhibit: The following are true with one of the TestKing routers:
1) The IOS image in flash is missing
2) No Network connectivity is available.
3) The router fallback IOS image is corrupt.
How will this Cisco 2600 series router respond if the conditions listed in the exhibitexist during the boot process?
A. The router will enter setup mode.
B. The router will enter ROM monitor mode.
C. The router will enter global configuration mode.
D. The boot will hang until an IOS is available.
Answer: B
解法: 进入监控模式，因为FLASH里的IOS损坏，再加上网络连接不可用，FLASH - TFTP - ROM
5. Which of the following statements regarding the use of multiple access lists are valid When configuring a single interface on a Cisco router?
A. Application of up to three access lists per protocol to a single interface.
B. No more than two access lists per interface.
C. One access list may be configured per direction for each Layer 3 protocol configured on an interface.
D. The maximum number allowed varies due to RAM availability in the router.
E. An infinite number of access lists that can be applied to an interface, from most specific to most general.
F. Cisco IOS allows only one access list to an interface.
Answer: C
解法: 多访问列表配置在单一接口下的正确描述，一条访问列表可以同时配置在一个三层接口的每个方向上（IN和OUT）。
6. A network addministrator wants to control which user hosts can access the network based on their MAC address . What will prevent workstations with unauthorized MAC address from connecting to network through a switch?
A.BPDU
B.Port security
C.RSTP
D.STP
E.VTP
F.Blocking mode
Answer: B
解法: 一个网络管理员想基于mac地址来控制网络的访问，下面哪个什么可以防止不授权的mac地址主机通过switch访问网络: 端口安全。
7.After the show ip route command has been entered , the following routes are displayec.Which route will not be entered into the routing table of a neichboring router?
A. R 192.168.8.0/24 via 192.168.2.2 ,00:00:10,Serial0
B. R 192.168.1.1/24 via 192.168.9.1 ,00:00:03,Serial1
C. C 192.168.1.0/24 is direotly connected,Echernet0
D. R 192.168.5.0/24 via 192.168.2.2 ,00:00:10,Serial0Answer: D
解法：问哪条路由不会出现在邻居路由器的路由表中，192.168.5.0/24 本地收到的metric是15跳，传给邻居变16跳就挂了
8.One type of frame switching uses low-latency forwarding and then switches to a higher-latency error checking mode when an error threshold is exceeded. What is the name of this frame switching mode?
A. store and forward
B. fragment-free
C. adaptive cut-through
D. fast-forward
Answer: C
解法：这题说的是一种自适应的直通转发模式，默认时使用低时延转发，当超过一个错误门限值后转变为高时延错误检查模式。
9.Given the choices below, which address represents a unicast address?
A. 224.1.5.2
B. FFFF. FFFF. FFFF.
C. 192.168.24.59/30
D. 255.255.255.255
E. 172.31.128.255/18
Answer: E
解释：题目要求选出单播地址A是组播地址
B明显错误
D是广播地址 C. 192.168.24.59/30写成二进制地址：11000000.10101000.00011000.001110 11
注意用空格分开的位置，因是Mask是/30，现在看后面两位是不是全为1，所以它也是广播地址。
10.Study the Exhibit below carefully: London#show vtp
VTP Version: 2
Configuration Revision: 0
Maximum VLANs supported locally: 64
Number of existing VLANs: 5
VTP Operating Mode: Client
VTP Domain Name: London
VTP Pruning Mode: Disabled
VTP V2 Mode: Disabled
VTP Traps Generation: Disabled
Based on the information given above, what is the VTP function of this particular
switch?
A. Learn and save VTP configuration in the running configuration.
B. Create and change VLANs.
C. Passes information about VTP configuration.
D. VTP is disabled on this device.
E. VTP is not saved to NVRAM.
Answer: A
解法：A答案较接近．学习和保存VTP的配置．B答案是典型的Server mode的功能；C答案是Transparent mode的功能；D答案是由于题中提到VTP Pruning Mode: Disabled
VTP V2 Mode: Disabled
VTP Traps Generation: Disabled，而来混淆选题者，VTP协议默认总是开着的！
E答案VTP is not saved to NVRAM是错的，因为1900交换机只有NVRAM，它的runningconfig就保存在NVRAM中。
11.Which of the following statements correctly describes the characteristics of a Frame Relay point-to-point subinterface? (Select two answer choices)
A. Needs to use Inverse ARP.
B. Maps a single IP subnet per DLCI.
C. Maps a single IP subnet across multiple DLCIs.
D. Resolves NBMA (non broadcast multi access) split horizon issues.
E. Requires use of the frame-relay map command.
F. None of the above
Answer: B D
解释：帧中继的Point-to-point要求每个子网要有属于自己的DLCI号，默认情况下，只有主接口才会识别DLCI，因而要给子接口分配相应的DLCI．而且这种类型可以解决水平分割的问题．
12.Which of the following correctly describe characteristics of PPP? (Select all valid answer choices)
A. Encapsulates several different types of routing protocols.
B. Supports only IP.
C. Can be used over analog circuits.
D. Is proprietary to Cisco
E. Supports error
Answer: A C E
解释：PPP只是用来封装用，支持多种的三层路由协议，Ｃ选项是说可以用于模拟线路，比如说电话播号等程控封装．并且提供了错误检测的能力，最后一个答案．
13.Regarding PAR (Positive Acknowledgement and Re-transmission), which of the answer choices below are correct? (Select all that apply.)
A. The source device will only retransmit lost packets on the request of
the destination device.
B. The source device starts a timer when it sends a segment and retransmits if an acknowledgment is not received before the timer expires.
C. The destination device acknowledges receipt of a segment by sending a packet with a new sequence number and the ACK bit sent.
D. The destination device acknowledges receipt of a segment by sending a packet that indicates the next sequence number it expects.
E. If the destination device does not receive a segment, all segments are retransmitted.
F. The source device keeps a record of all segments sent and expects and acknowledgment of each.
Answer: B D F
解释：Positive Acknowledgement and Re-transmission 带确认的肯定重传，要求接收方机器在收到数据时，通过向发送方回送一个确认消息，来与发送发机器保持通信．发送方将它所收到的每个数据段都记录下来，并在发送下一个数据段之前，等待对它们的确认．当发送一个数据段时，发送方机器启动一个计时器，如果在收到从接收方返回的确认之前计时器到期了，就重传这个数据段．
14.When selecting a Network Interface Card (NIC), which of the following factors need to be considered? Select three
A. The type of application used on the network
B. The type of system bus used by the computers
C. The type of memory installed in each computer
D. The type of media used in the network topology
E. The type of protocols used in the network
F. The physical layout of the network hosts
Answer: B D E
解释：这题主要考察网卡的问题了．系统总线，媒体类型，网络协议（一般都是TCP/IP）
15.A new switch is installed in the Testking network. This switch is to be configured so that VLAN information will be automatically distributed to all the other Cisco Catalyst switches in the network.Which of the conditions below have to be met in order for this to occur? (Choose allthat apply).
A. The switch that will share the VLAN information must be in the VTP Server mode.
B. The switches must be in the same VTP domain.
C. The switch that will share the VLAN information must be configured as the root bridge.
D. The switches must be configured to use the same VTP version.
E. The switches must be configured to use the same STP version.
F. The switches must be configured to use the same type of ID tagging.
Answer: ABD
解释：共享VLAN的信息必须是server模式，即A;VTP工作也必须是在同一个DOMAIN当中;如果vtp version不同，那么相互之间也不能够传递VLAN的信息了。
16.You just purchased a refurbished router that contains a configuration from a previous deployment. What should you do, before entering a new configuration into the router?
A. RAM should be erased and the router restarted.
B. Flash should be erased and the router restarted.
C. NVRAM should be erased and the router restarted.
D. The new configuration should be entered and saved.
Answer: C
解释：题中的意思是说，买了一个二手路由器，里面有一些配置，问你要怎么做在输入新的配置之前，当然是应该将原先的配置删除er start-configure，然后再重启路由器reload。删除NVRAM里面的配置必须重启路由器才会生效，里面的配置才会删除。
17.You have a server that’s directly connected to a Cisco switch by way of its Fa0/1 port, and you don’t want any other MAC addresses from any other servers to access this port. How would you accomplish this? (Select two answer choices)
A. Configure port Fa0/1 to accept connections only from the static IP address of the server.
B. Employ a proprietary connector type on Fa0/1 that is incompatible with other host connectors.
C. Configure the MAC address of the server as a static entry associated with port Fa0/1.
D. Bind the IP address of the server to its MAC address on the switch to prevent other hosts from spoofing the server IP address.
E. Configure port security on Fa0/1 to reject traffic with a source MAC address other than that of the server.
F. Configure an access list on the switch to deny server traffic from entering any port other than Fa0/1.
Answer: C, E
解释：题中 don’t want any other MAC addresses为关键字，那个交换机的端口只允许server的MAC地址能够通过，其他的否。C答案是让那个端口绑定MAC地址，只允许MAC address of the server 能够进入。E是做端口安全，只允许来自源MAC（server)的流量进入。
18.A new switch is installed into an existing LAN and a new VTP trunk is set up with an existing switch. Which VLANs will be allowed on this new trunk?
A. All defined VLANs are allowed on the trunk by default.
B. Each VLAN, or VLAN range, that is specified with the switchport mode command.
C. Each VLAN, or VLAN range, that is specified with the vtp domain command.
D. Each VLAN, or VLAN range, that is specified with the vlan database
Answer: A
解释：对于CISCO的交换机来说，默认情况下，所有的VLAN都是允许通过TRUNK LINK。
19.When a new trunk link is configured on an IOS based switch, which VLANs are allowed over the link?
A. By default, all defined VLANs are allowed on the trunk.
B. Each single VLAN, or VLAN range, must be specified with the switchport mode command.
C. Each single VLAN, or VLAN range, must be specified with the vtp domain command.
D. Each single VLAN, or VLAN range, must be specified with the vlan database command.
Answer: A
解释：对于CISCO的交换机来说，默认情况下，所有的VLAN都是允许通过TRUNK LINK。
如果是华为交换机，需要加上一条trunk permit vlan all，这样才允许所有的VLAN通过。
20.You work as a network engineer at TestKing.com. TestKing users have noticed extremely slow network performance, intermittent connectivity, and loss of connection. After entering the show interfaces command, you notice that the Ethernet interface is configured as 100 Mbps full-duplex and that there is evidence of late collisions.
What could be the cause of this problem?
A. duplex mismatch
B. a routing loop
C. trunking mode mismatch
D. improperly configured root bridge
E. improperly configured static VLAN
Answer: A
解释：题意说明 as 100 Mbps full-duplex and that there is evidenceof late collisions.使用百兆全双工，出现了延时冲突的问题，说明另一端的双工设置与之不符。应都设为全双工的模式。
21.When designing OSPF networks;what is the purpose of using a hierarchical design?(Select all choices that apply)
A.To reduce the complexity of router configuration
B.To speed up convergence
C.To confine network instability to single areas of the network
D.To reduce routing overhead
E.To lower costs by replacing routers
F.To decrease latency
Answer: B C D
解释：ospf的分层管理的优点1、有利于快速收敛2、在一个单一的区域里限制不稳定性3、减少路由花费
22.A network administrator has been asked to set up a fully-meshed Frame Relay network to connect six remote research sites.How many PVCs are required in this network?
A. 6
B. 15
C. 18
D. 36
E. 41
Answer B
解释：设计一个全网状互联帧中继网络，六个站点，需要多少条PVC，公式是：N*(N-1)/2
23.Routers perform which of the following functions? (Select three)
A. Packet switching
B. Collision prevention on a LAN segment.
C. Packet filtering
D. Broadcast domain enlargement
E. Broadcast forwarding
F. Internetwork communication
Answer: A C F
解释：这题要求选路由器的功能A 包的交换B 在局域网上阻止冲突C 包过滤D广播域的放大E广播转发F 网间通讯
24. The Testking corporate LAN consists of one large flat network. You decide to segment this LAN into two separate networks with a router. What will be the affect of this change?
A. The number of broadcast domains will be decreased.
B. It will make the broadcasting of traffic between domains more efficient between segments.
C. It will increase the number of collisions.
D. It will prevent segment 1's broadcasts from getting to segment 2.
E. It will connect segment 1's broadcasts to segment 2.
Answer: D
解释：这个题目问用一个路由器把一个网络一分为二,那么会发生什么样的改变?
A 广播域的数量将被减少(错,增加) B 胡言乱语 C 增加了冲突的数量(减少) D阻止了广播,是对的 E传输广播,不对
25. With regard to bridges and switches, which of the following statements are true?(Choose three.)
A. Switches are primarily software based while bridges are hardware based.
B. Both bridges and switches forward Layer 2 broadcasts.
C. Bridges are frequently faster than switches.
D. Switches typically have a higher number of ports than bridges.
E. Bridges define broadcast domain while switches define collision domains.
F. Both bridges and switches make forwarding decisions based on Layer 2 addresses.
Answer: B D F
解释：交换机和桥之间的相同点和区别?
相同点：桥和交换机都是二层设备
不同点:交换机是硬件的,桥是软件,所以交换机的速度要比桥快很多交换机的端口数目要比桥多,一般来说,桥的端口数目不会超过16个
占位更新 1# 占位更新 2# 占位更新 3# 我晕。如来佛祖大名如雷灌耳。整理的好啊。帖子开的也好。
大家以后有关NA TK的问题都往这边发。 非常好
这贴我顶了 好多问题
偷看了那么久，还是给ＬＺ顶顶 顶不用自己翻译了 LZ辛苦了!非常感谢! 顶～
辛苦啦
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