CCNA（200-125）题库V3.0(2018.08.07) CCNA（200-125）题库V3.0（2018.08.07）

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CCNA（200-125）题库V3.0(2018.08.07)
Number: 200-125
Passing Score: 810
Time Limit: 120 min
File Version: v3.0
CCNA（200-125）题库V3.0（2018.08.07）
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注意：思科发布最新的CCNA版本是V3.0，考试代号200-125，V3.0为目前最新官方正版题库，
思科目前并没有发布V3.1、V4.0等版本。
更新内容：
修改错误答案
增加新题
=============================================
Sections
1. part 1
2. part 2
3. part 3
选择拖图题
QUESTION 1
Which technology supports the stateless assignment of IPv6 addresses?(Choose two.)
A. DNS
B. DHCPv6
C. DHCP
D. autoconfiguration
Correct Answer: BD
Section: part 1
Explanation
Explanation/Reference:
QUESTION 2
After you configure the Loopback0 interface, which command can you enter to verify the
status of the interface and determine whether fast switching is enabled?
A. Router#show ip interface loopback 0
B. Router#show run
C. Router#show interface loopback 0
D. Router#show ip interface brief
Correct Answer: A
Section: part 1
Explanation
Explanation/Reference:
QUESTION 3
What are two requirements for an HSRP group? (Choose two.)
A. exactly one active router
B. one or more standby routers
C. one or more backup virtual routers
D. exactly one standby active router
E. exactly one backup virtual router
Correct Answer: AD
Section: part 1
Explanation
Explanation/Reference:
QUESTION 4
Which command sequence can you enter to create VLAN 20 and assign it to an interface
on a switch?
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A. Switch(config)#vlan 20
Switch(config)#Interface gig x/y
Switch(config-if)#switchport access vlan 20
B. Switch(config)#Interface gig x/y
Switch(config-if)#vlan 20
Switch(config-vlan)#switchport access vlan 20
C. Switch(config)#vlan 20
Switch(config)#Interface vlan 20
Switch(config-if)#switchport trunk native vlan 20
D. Switch(config)#vlan 20
Switch(config)#Interface vlan 20
Switch(config-if)#switchport access vlan 20
E. Switch(config)#vlan 20
Switch(config)#Interface vlan 20
Switch(config-if)#switchport trunk allowed vlan 20
Correct Answer: A
Section: part 1
Explanation
Explanation/Reference:
QUESTION 5
Which three commands can you use to set a router boot image? (Choose three.)
A. Router(config)# boot system flash c4500-p-mz.121-20.bin
B. Router(config)# boot system tftp c7300-js-mz.122-33.SB8a.bin
C. Router(config)#boot system rom c7301-advipservicesk9-mz.124-24.T4.bin
D. Router> boot flash:c180x-adventerprisek9-mz-124-6T.bin
E. Router(config)#boot flash:c180x-adventerprisek9-mz-124-6T.bin
F. Router(config)#boot bootldr bootflash:c4500-jk9s-mz.122-23f.bin
Correct Answer: ABC
Section: part 1
Explanation
Explanation/Reference:
QUESTION 6
Which two statements about IPv6 and routing protocols are true? (Choose two.)
A. EIGRPv3 was developed to support IPv6 routing.
B. OSPFv3 was developed to support IPv6 routing.
C. Loopback addresses are used to form routing adjacencies.
D. EIGRP, OSPF, and BGP are the only routing protocols that support IPv6.
E. Link-local addresses are used to form routing adjacencies.
Correct Answer: BE
Section: part 1
Explanation
Explanation/Reference:
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QUESTION 7
If primary and secondary root switches with priority 16384 both experience catastrophic
losses, which tertiary switch can take over?
A. a switch with priority 20480
B. a switch with priority 8192
C. a switch with priority 4096
D. a switch with priority 12288
Correct Answer: A
Section: part 1
Explanation
Explanation/Reference:
题目前提是优先级16384是跟桥，所有其他交换机优先级必须大于16384才能使其成为跟桥
QUESTION 8
Which two statements about late collisions are true? (Choose two.)
A. They may indicate a duplex mismatch.
B. By definition, they occur after the 512th bit of the frame has been transmitted.
C. They indicate received frames that did not pass the FCS match.
D. They are frames that exceed 1518 bytes.
E. They occur when CRC errors and interference occur on the cable.
Correct Answer: AB
Section: part 1
Explanation
Explanation/Reference:
QUESTION 9
Which command can you enter to set the default route for all traffic to an interface?
A. router(config)#ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1
B. router(config)#ip route 0.0.0.0 255.255.255.255 GigabitEthernet0/1
C. router(config-router)#default-information originate
D. router(config-router)#default-information originate always
Correct Answer: A
Section: part 1
Explanation
Explanation/Reference:
QUESTION 10
Which two spanning-tree port states does RSTP combine to allow faster convergence?
(Choose two.)
A. blocking
B. listening
C. learning
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D. forwarding
E. discarding
Correct Answer: AB
Section: part 1
Explanation
Explanation/Reference:
STP定义了5种不同的端口状态，关闭(disable)，监听（Listening），学习（Learning），阻断（Blocking）
和转发（Forwarding）
在RSTP中只有三种端口状态，Discarding、Learning和Forwarding
QUESTION 11
If a router has four interfaces and each interface is connected to four switches, how
many broadcast domains are present on the router?
A. 1
B. 2
C. 4
D. 8
Correct Answer: C
Section: part 1
Explanation
Explanation/Reference:
QUESTION 12
Which command enables IPv6 forwarding on a cisco router?
A. ipv6 host
B. ipv6 unicast-routing
C. ipv6 local
D. ipv6 neighbor
Correct Answer: B
Section: part 1
Explanation
Explanation/Reference:
在路由器上激活IPV6的命令
QUESTION 13
Refer to the exhibit. What is the most appropriate summarization for these routes?
A. 10.0.0.0 /21
B. 10.0.0.0 /22
C. 10.0.0.0 /23
D. 10.0.0.0 /24
Correct Answer: B
Section: part 1
Explanation
Explanation/Reference:
考点分析：这道题考的是子网的聚合。
10.0. 0 0 0 0 0 0 0 0 .0
10.0. 0 0 0 0 0 0 0 1 .0
10.0. 0 0 0 0 0 0 1 0 .0
10.0. 0 0 0 0 0 0 1 0 .0
十进制转成二进制， 发现这四个网段前22位都是一致的，故选项 为B。
QUESTION 14
Which set of commands is recommended to prevent the use of a hub in the access layer?
A. switch(config-if)#switchport mode trunk
switch(config-if)#switchport port-security maximum 1
B. switch(config-if)#switchport mode trunk
switch(config-if)#switchport port-security mac-address 1
C. switch(config-if)#switchport mode access
switch(config-if)#switchport port-security maximum 1
D. switch(config-if)#switchport mode access
switch(config-if)#switchport port-security mac-address 1
Correct Answer: C
Section: part 1
Explanation
Explanation/Reference:
防止集线器在接入层交换机上使用需要下列那个命令？
考点分析：这道题考的是端口安全，怎么限制集线器的使用，即是只允许在交换机的接口上连一个终端设
备。
QUESTION 15
A router has learned three possible routes that could be used to reach a destination network. One route is
from EIGRP and has a composite metric of 20514560. Another route is from OSPF with a metric of 782.
The last is from RIPv2 and has a metric of 4. Which route or routes will the router install in the routing
table?
A. the OSPF route
B. the EIGRP route
C. the RIPv2 route
D. all three routes
E. the OSPF and RIPv2 routes
Correct Answer: B
Section: part 1
Explanation
Explanation/Reference:
考点：考查路由条目进入路由表的原则：最优路由才能进入。去往同一目的的多条路由，先比较AD值，AD
值小者优先；AD值一直则比较metric值。
AD值：
EIGRP 90
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OSPF 110
RIP 120
QUESTION 16
Two routers named Atlanta and Brevard are connected via their serial interfaces as illustrated, but they are
unable to communicate. The Atlanta router is known to have the correct configuration.
Given the partial configurations, identify the fault on the Brevard router that is causing the lack of
connectivity.
A. incompatible IP address
B. insufficient bandwidth
C. incorrect subnet mask
D. incompatible encapsulation
E. link reliability too low
F. IPCP closed
Correct Answer: D
Section: part 1
Explanation
Explanation/Reference:
两个路由器端口封装不一致，一个是HDLC，一个是PPP
QUESTION 17
A network administrator needs to configure a serial link between the main office and a remote location.The
router at the remote office is a non-cisco router. How should the network administrator configure the serial
interface of the main office router to make the connection?
A. Main(config)#interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#no shut
B. Main(config)#interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#encapsulation ietf
Main(config-if)#no shut
C. Main(config)#interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#encapsulation frame-relay
Main(config-if)#authenication chap
Main(config-if)#no shut
D. Main(config)#interface serial 0/0
Main(config-if)#ip address 172.16.1.1 255.255.255.252
Main(config-if)#encapsulation ppp
Main(config-if)#no shut
Correct Answer: D
Section: part 1
Explanation
Explanation/Reference:
remote office 使用非思科路由器，则main office 是思科路由器。
HDLC是Cisco路由器在同步串行线路上的默认封装方式。每个厂商的HDLC都是专用的。
PPP 用于异步串行（拨号）或同步串行（isdn）介质。PPP的基本目标是在数据链路层点到点链路上传输
第3层包。它不是一个专用协议，这就意味着如果你的路由器并不都是Cisco的，可以在串行接口上配置
PPP封装。串行接口两端的路由器都配置PPP才能工作。
帧中继有两种封装类型----Cisco和IETF.除非手动输入IETF，否则默认封装是Cisco。如果用帧中继连接一条
Cisco设备和一条非Cisco设备，要选择IETF封装类型。命令格式如下
Router(config)#int s0/0/0
Router(config-if)#encapsulation ?
frame-relay Frame Relay networks
hdlc Serial HDLC synchronous
ppp Point-to-Point protocol
Router(config-if)#encapsulation frame-relay ?
ietf Use RFC1490/RFC2427 encapsulation
<cr>
由此判断选项B 和C，命令格式不正确。
如果当一台思科路由器和一台非思科路由器通过串行连接在一起时，必须配置PPP或另外一种封装方法，像
帧中继，因为默认的HDLC不能工作。
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QUESTION 18
Which layer 2 protocol encapsulation type supports synchronous and asynchronous circuis and has built-in
security mechanisms?
A. Frame Relay
B. HDLC
C. x.25
D. PPP
Correct Answer: D
Section: part 1
Explanation
Explanation/Reference:
哪一个二层协议封装支持同步和异步电路并内嵌安全机制？
答案：PPP
QUESTION 19
Refer to the exhibit. The two connected ports on the switch are not turning orange or green. What would be
the most effective steps to troubleshoot this physical layer problem? (Choose three.)
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A. Ensure that the Ethernet encapsulations match on the interconnected router and switch ports.
B. Ensure that cables A and B are straight-through cables.
C. Ensure cable A is plugged into a trunk port.
D. Ensure the switch has power.
E. Reboot all of the devices.
F. Reseat all cables.
Correct Answer: BDF
Section: part 1
Explanation
Explanation/Reference:
考点：考查交换机端口颜色的定义。绿色正常，橘黄色有故障。
A：确认以太网封装是否匹配，错误。封装错误不会在端口LED显示
B：确认线缆A/B是否为直通线，正确。异构设备使用直通线
C：确认线缆A是否插到trunk口，错误。
D：确认是否通电，正确。
E：重启设备，错误。
F：重置所有电缆，正确。
QUESTION 20
A network administrator is troubleshooting the OSPF configuration of routers R1 and R2. The routers
cannot establish an adjacency relationship on their common Ethernet link. The graphic shows the output of
the show ip ospf interface e0 command for routers R1 and R2. Based on the information in the graphic,
what is the cause of this problem?
A. The OSPF area is not configured properly.
B. The priority on R1 should be set higher.
C. The cost on R1 should be set higher.
D. The hello and dead timers are not configured properly.
E. A backup designated router needs to be added to the network.
F. The OSPF process ID numbers must match.
Correct Answer: D
Section: part 1
Explanation
Explanation/Reference:
QUESTION 21
What will happen if a private IP address is assigned to a public interface connected to an ISP?
A. Addresses in a private range will be not routed on the Internet backbone.
B. Only the ISP router will have the capability to access the public network.
C. The NAT process will be used to translate this address in a valid IP address.
D. Several automated methods will be necessary on the private network.
E. A conflict of IP addresses happens, because other public routers can use the same range.
Correct Answer: A
Section: part 1
Explanation
Explanation/Reference:
私有地址被分配到连接到ISP的公网端口上，将会发生什么？
内部网络使用了私有地址，如果不使用nat的话我们是没办法访问外部网络的。因为公共网络不会给私有地
址路由
QUESTION 22
Refer to the exhibit. The Bigtime router is unable to authenticate to the Littletime router. What is the cause
of the problem?
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