【CCNA解析】专题二 路由相关知识

林原静羽

本次专题讲解的是和路由相关知识（题目从V.31中抽取）。先上题目和解析，图以后补齐。
4. Refer to the exhibit. Which two statements are true about the loopback address that is configured on
RouterB? (Choose two.)
A. It ensures that data will be forwarded by RouterB.
B. It provides stability for the OSPF process on RouterB.
C. It specifies that the router ID for RouterB should be 10.0.0.1.
D. It decreases the metric for routes that are advertised ** RouterB.
E. It indicates that RouterB should be elected the DR for the LAN.
翻译：参考图，关于RouterB的环回口哪两个描述是正确的？
A.它确保数据将会被RouterB转发。
B.它为RouterB的OSPF进程提供稳定性。
C.它指定了RouterB的router ID为10.0.0.1。
D.它减少了RouterB通告路由的度量值。
E.它表明RouterB应该是这个LAN的DR。
解析:涉及的知识点，运行OSPF进程的路由器自动选举router ID时，若有环回口则选择最高的环回口IP，B中只有一个环回口，即10.0.0.1为router ID.由于环回口是逻辑接口，保证了OSPF进程的稳定性。选项A、D、E不符合。一个LAN中选择DR，先比较优先级再比较 router-id，越大越优先。
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9. Refer to the exhibit. The router has been configured with these commands:
hostname Gateway
interface FastEthernet 0/0
ip address 198.133.219.14 255.255.255.248
no shutdown
interface FastEthernet 0/1
ip address 192.168.10.254 255.255.255.0
no shutdown
interface Serial 0/0
ip address 64.100.0.2 255.255.255.252
no shutdown
ip route 0.0.0.0 0.0.0.0 64.100.0.1
What are the two results of this configuration? (Choose two.)
A. The default route should have a next hop address of 64.100.0.3.
B. Hosts on the LAN that is connected to FastEthernet 0/1 are using public IP addressing.
C. The address of the subnet segment with the WWW server will support seven more servers.
D. The addressing scheme allows users on the Internet to access the WWW server.
E. Hosts on the LAN that is connected to FastEthernet 0/1 will not be able to access the Internet without
address translation.
翻译：路由器上配置下列命令，这些配置会出现哪两个结果？
A.默认路由下一跳IP为64.100.0.3
B.LAN中与f0/1直连的主机使用公有IP地址。
C.WWW服务器所在子网的地址将支持多于7种的服务。
D.该地址方案允许Internet上的用户访问WWW服务器。
E.LAN中与f0/1直连的主机在没有地址转换时无法访问Internet.
解析：此题考察的是私有、公有地址识别（见专题一）以及默认路由的语法格式。ip route 0.0.0.0 0.0.0.0 64.100.0.1这条命令表示默认路由下一跳IP为64.100.0.1。A错。
interface FastEthernet 0/1
ip address 192.168.10.254 255.255.255.0
这两条命令表示f0/1使用地址192.168.10.254，为私有地址，所以直连的主机也为私有地址，需要NAT才能访问Internet.故B错，E对。WWW服务器提供http服务，无所谓7种服务等。故C错。WWW服务器的地址为198.133.219.14，为公有地址，故可以被Internet上的用户访问。故D对。选项为DE。
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12. Which two statements are true about the command ip route 172.16.3.0 255.255.255.0 192.168.2.4?
(Choose two.)
A. It establishes a static route to the 172.16.3.0 network.
B. It establishes a static route to the 192.168.2.0 network.
C. It configures the router to send any traffic for an unknown destination to the 172.16.3.0 network.
D. It configures the router to send any traffic for an unknown destination out the interface with the address
192.168.2.4.
E. It uses the default administrative distance.
F. It is a route that would be used last if other routes to the same destination exist.
翻译：关于命令ip route 172.16.3.0 255.255.255.0 192.168.2.4哪两个描述是正确的？
A.它建立去往172.16.3.0网段的静态路由。
B.它建立去往192.168.2.0网段的静态路由。
C.配置使得路由器发送未知目的IP的流量去往172.16.3.0网段。
D.配置使得路由器将未知目的地的流量从IP地址为192.168.2.4的接口发送出去。
E.它使用默认的AD值。
F.去往同一个目的地有其他路由时，这条路由会被最后使用。
解析：考察对静态路由的理解。这条命令表示去往172.16.3.0 网段的流量发往192.168.2.4的下一跳。使用的是默认的AD值1。正确选项为AE。
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16. Refer to the exhibit. Assume that the routing protocol referenced in each choice below is configured with
its default settings and the given routing protocol is running on all the routers. Which two conditional
statements accurately state the path that will be chosen between networks 10.1.0.0 and 10.3.2.0 for the
routing protocol mentioned? (Choose two.)
A. If OSPF is the routing protocol, the path will be ** R1 to R3 to R4 to R5.
B. If OSPF is the routing protocol, the path will be ** R1 to R2 to R5.
C. If OSPF is the routing protocol, the path will be ** R1 to R5.
D. If RIPv2 is the routing protocol, the path will be ** R1 to R3 to R4 to R5.
E. If RIPv2 is the routing protocol, the path will be ** R1 to R5.
翻译：参考图，各个选项中假设路由器上运行不同的路由协议，关于去往网段10.1.0.0和10.3.2.0的选路哪两个是正确的？
解析：此题考察的是各个路由协议的metric度量值计算方式。OSPF协议的metric值为cost，cost=10^8/带宽，cost与带宽成反比，选R1-R3-R4-R5。RIPv2的metric值为hop,跳数，选R1-R5。正确选项为AE。
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21. Refer to the exhibit. Which three statements are true about how router JAX will choose a path to the 10.1.3.0/24 network when different routing rotocols are configured? (Choose three.)
A. By default, if RIPv2 is the routing protocol, only the path JAX-ORL will be installed into the routing table.
B. The equal cost paths JAX-CHI-ORL and JAX-NY-ORL will be installed in the routing table if RIPv2 is the
routing protocol.
C. When EIGRP is the routing protocol, only the path JAX-ORL will be installed in the routing table by
default.
D. When EIGRP is the routing protocol, the equal cost paths JAX-CHI-ORL, and JAX-NY-ORL will be
installed in the routing table by default.
E. With EIGRP and OSPF both running on the network with their default configurations, the EIGRP paths
will be installed in the routing table.
F. The OSPF paths will be installed in the routing table, if EIGRP and OSPF are both running on the
network with their default configurations.
翻译：参考图，当配置不同路由协议时，路由器JAX去往10.1.3.0/24网段是怎么选路的？
解析：考察点同上题，不同协议的metric值，以及同时使用不同协议时根据AD值选路。使用RIPv2,选择JAX-ORL。EIGRP metric为五个复合值，与带宽成反比，支持等价负载均衡，即JAX-NY-ORL和JAX-CHI-ORL两条形成等价负载均衡。同时使用EIGRP和OSPF时，由于EIGRP AD为90，OSPF AD值为110,故选择EIGRP。正确选项为ADE。
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22. Refer to the exhibit. Which three statements correctly describe Network Device A? (Choose three.)
A. With a network wide mask of 255.255.255.128, each interface does not require an IP address.
B. With a network wide mask of 255.255.255.128, each interface does require an IP address on a unique IP
subnet.
C. With a network wide mask of 255.255.255.0, must be a Layer 2 device for the PCs to communicate with
each other.
D. With a network wide mask of 255.255.255.0, must be a Layer 3 device for the PCs to communicate with
each other.
E. With a network wide mask of 255.255.254.0, each interface does not require an IP address.
翻译：参考图，关于网络设备A哪三个描述是正确的？
A.若掩码为255.255.255.128，则每个接口不需要配置IP。
B.若掩码为255.255.255.128，则每个接口需要配置IP。
C.若掩码为255.255.255.0，一定是使用二层设备连接两PC。
D.C.若掩码为255.255.255.0，一定是使用三层设备连接两PC。
E.若掩码为255.255.254.0，每个接口需要配置IP地址。
解析：考察VLSM，不同子网的判断方法。若两PC是在同一个网段，不需要另外配置IP地址，中间的设备为二层设备，若两PC在不同的网段，则中间的设备为三层设备，需要配置IP地址。当掩码为255.255.255.128/255.255.255.0，两PC均属于不同的网段，故中间设备为三层设备，且需要IP地址。为掩码为255.255.254.0，两PC位于同一个子网10.1.0.0/23（范围：10.1.0.1——10.1.1.254，具体计算方法参考专题一），中间设备为二层设备即可，不需要配置IP。
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25. Refer to the exhibit. The network administrator must establish a route by which London workstations
can forward traffic to the Manchester workstations. What is the simplest way to accomplish this?
A. Configure a dynamic routing protocol on London to advertise all routes to Manchester.
B. Configure a dynamic routing protocol on London to advertise summarized routes to Manchester.
C. Configure a dynamic routing protocol on Manchester to advertise a default route to the London router.
D. Configure a static default route on London with a next hop of 10.1.1.1.
E. Configure a static route on London to direct all traffic destined for 172.16.0.0/22 to 10.1.1.2.
F. Configure Manchester to advertise a static default route to London.
翻译：参考图，网络管理员建立路由条目确定London工作站可以转发流量到Manchester 工作站。下列哪个是最简单的方法？
A.在London上配置动太路由协议通告所有的路由条目给Manchester。
B.在London上配置动太路由协议通告汇总路由条目给Manchester。
C.在Manchester上配置动太路由协议通告默认路由条目给London。
D.在London上配置下一跳为10.1.1.1的默认路由。
E.在London上配置静态路由将去往172.16.0.0/22网段的流量发到10.1.1.2。
解析：考察静态路由的优点：简单。故排除掉ABC。在London上配置静态路由，下一跳为10.1.1.2，故选 E.
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103. Your ISP has given you the address 223.5.14.6/29 to assign to your router's interface. They have also given you the default gateway address of 223.5.14.7. After you have configured the address, the router is unable to ping any remote devices. What is preventing the router ** pinging remote devices?
A. The default gateway is not an address on this subnet.
B. The default gateway is the broadcast address for this subnet.
C. The IP address is the broadcast address for this subnet.
D. The IP address is an invalid class D multicast address.
翻译:ISP为你的路由器接口分配地址223.5.14.6/29，并告诉你的网关地址为223.5.14.7，配置后发现路由器无法ping通远端设备，哪些原因防止路由器ping通远端设备？
A.默认网关不在同一个子网。
B.默认网关是该子网的广播地址。
C.接口IP地址为子网的广播地址。
D.接口IP地址为D类组播地址。
解析：考察IP地址。接口IP地址属于子网223.5.14.0/29，该子网的范围：223.5.14.0——223.5.14.7，223.5.14.7为广播地址。D类地址从224.0.0.0开始。故选项为B。
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107. Which command is used to configure a default route?
A. ip route 172.16.1.0 255.255.255.0 0.0.0.0
B. ip route 172.16.1.0 255.255.255.0 172.16.2.1
C. ip route 0.0.0.0 255.255.255.0 172.16.2.1
D. ip route 0.0.0.0 0.0.0.0 172.16.2.1
翻译：配置默认路由的是哪条命令？
考察：默认路由的配置，选D。
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108. If IP routing is enabled, which two commands set the gateway of last resort to the default gateway?
(Choose two.)
A. ip default-gateway 0.0.0.0
B. ip route 172.16.2.1 0.0.0.0 0.0.0.0
C. ip default-network 0.0.0.0
D. ip default-route 0.0.0.0 0.0.0.0 172.16.2.1
E. ip route 0.0.0.0 0.0.0.0 172.16.2.1
翻译：如果配置IP路由，哪两条命令可以设置默认网关?
解析：考察路由器默认网关的设置。对于路由器来说，默认路由中指明的下一跳即为路由器的网关，选项为CE。
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114. What must be set correctly when configuring a serial interface so that higher-level protocols calculate
the best route?
A. bandwidth
B. delay
C. load
D. reliability
翻译：serial接口下，高级路由协议如何计算最优路由？
解析：带宽。

林原静羽

139. Refer to the exhibit. Which (config-router) command will allow the network represented on the interface to be advertised by RIP?
A. redistribute ethernet0
B. network ethernet0
C. redistribute 10.12.0.0
D. network 10.12.0.0
翻译：参考图，哪条(config-router)模式下的命令允许ethernet0接口表示的10.12.0.0/16网段被RIP宣告。
解析：考察RIP进程如何宣告网段。选D.
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140. Refer to the exhibit. What information can be gathered ** the output?
A. One router is running RIPv1.
B. RIP neighbor is 224.0.0.9.
C. The network contains a loop.
D. Network 10.10.1.0 is reachable.
翻译：参考图，从输出消息中可得到哪些信息？
A.一个路由器是运行RIPv1.
B.RIP邻居是224.0.0.9。
C.网络包含一个环回口。
D.网段10.10.1.0是可达的。
解析：考察RIP发送更新和生成路由表的过程。从debug消息知，"sending v2 flash"表明运行RIPv2,RIPv2是利用224.0.0.9组播地址更新。选项AB错，debug第四行消息"sending v2 flash ** to 224…… via loopback0 (10.10.1.1)" 以及第八行"ignored v2 packet ** 10.10.1.1(source ** one of our addresses)"表明10.10.1.1这个环回口并不是在本地网络中。第三、六、七行消息"buidl flash……"表明生成三条路由条目。即10.10.1.0出现在本地路由表中，即可达的。故选D。
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147. Refer to the exhibit. Which value will be configured for Default Gateway of the Local Area Connection?
A. 10.0.0.0
B. 10.0.0.254
C. 192.223.129.0
D. 192.223.129.254
翻译：参考图，哪个配置为本地连接的网关？
解析：考察PC 的IP地址与网关的关系。尽管default gateway没有填写，但由于IP地址为10.0.0.249/24，根据排除法知网关为10.0.0.254.选B。
148. Refer to the exhibit. The user at Workstation B reports that Server A cannot be reached. What is
preventing Workstation B ** reaching Server A?
A. The IP address for Server A is a broadcast address.
B. The IP address for Workstation B is a subnet address.
C. The gateway for Workstation B is not on the same subnet.
D. The gateway for Server A is not on the same subnet.
翻译：参考图，工作站B的用户报告说服务器A无法访问，哪些原因防止工作站B访问服务器A。
解析：考察VLSM知识，和PC、网关之间的关系。工作站B IP为131.1.123.43/27，所在子网为131.1.123.32，可用IP范围为131.1.123.33——131.1.123.62.服务器A的IP为131.1.123.24/27，属于子网131.1.123.0/27，可用IP范围为131.1.123.1——30,故服务器A的IP与网关不在同一个子网，选D.
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166. Use the output ** the router shown in the graphic above to determine which of the following are correct. (Choose two.)
A. Router John uses a link-state routing protocol.
B. Router John will receive routing **s on the Serial0/0 interface.
C. Router John will receive routing **s on the Serial0/1 interface.
D. Router John will send routing **s out the Serial0/0 interface.
E. Router John will send routing **s out the FastEthernet0/0 interface.
F. Router John will send routing **s out the Serial0/1 interface
翻译：根据输出消息判断下列哪两个选项是正确的？
解析：考察通过"show ip protocol" "show ip interface brief"获取RIP协议的相关信息。由"routing protocol is rip"知路由协议是RIP，RIP是距离矢量路由协议，故A错。由"routing for networks: 10.0.0.0"知宣告的是10.0.0.0即将s0/0（IP为10.168.11.17）宣告进RIP进程，即从s0/0接收和发送路由更新。故正确选项为BD。
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171. OSPF routing uses the concept of areas. What are the **acteristics of OSPF areas? (Choose three.)
A. Each OSPF area requires a loopback interface to be configured.
B. Areas may be assigned any number ** 0 to 65535.
C. Area 0 is called the backbone area.
D. Hierarchical OSPF networks do not require multiple areas.
E. Multiple OSPF areas must connect to area 0.
F. Single area OSPF networks must be configured in area 1.
翻译：OSPF使用区域的概念，哪些是OSPF 区域的特点？
A.每个OSPF区域需配置一个环回口。
B.区域可以指定为0到65535.
C.area 0被称为骨干区域。
D.层次化的OSPF网络不需要多区域。
E.多区域需与area0直连。
F.OSPF单区域必须配为area 1.
解析：考察OSPF 层次化，划分多区域的特点。OSPF区域分为area0 即骨干区域，非area0即常规区域。单区域时可以正常通信，不一定要配置成area 0，多区域时必须有area 0且非area 0需紧邻着area 0.故选项为BCE。
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172. What information does a router running a link-state protocol use to build and maintain its topological database? (Choose two.)
A. hello packets
B. SAP messages sent by other routers
C. LSAs ** other routers
D. beacons received on point-to-point links
E. routing tables received ** other link-state routers
F. TTL packets ** designated routers
翻译：哪些信息说明运行链路状态路由协议的路由怎么建立和维护拓扑数据库？
解析：考察对链路状态拓扑表的理解。CCNA学过的链路状态路由协议为OSPF。OSPF通过交换hello包建立、维护邻居关系，邻居之间交换LSA（链路状态信息）生成拓扑数据库。即选项为AC。
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173. Which statements describe the routing protocol OSPF? (Choose three.)
A. It supports VLSM.
B. It is used to route between autonomous systems.
C. It confines network instability to one area of the network.
D. It increases routing overhead on the network.
E. It allows extensive control of routing **s.
F. It is simpler to configure than RIP v2.
翻译：关于OSPF协议哪些描述是正确的？
A.支持VLSM。
B.在AS间使用。
C.将网络中的不稳定性局限在单区域内。
D.增加了网络上的路由负载。
E.允许广泛的控制路由更新。
F.比RIPv2配置更简单。
解析：解析：考察OSPF协议的特征。支持VLSM，A正确;无法配置AS号，B错误;由于使用区域的概念将不稳定性局限在单区域中，C对;增加了网络上的路由负担，OSPF有相应的优化措施，不一定会增加路由负担。比起RIP配置更复杂，故F错，正确选项为ACE。

anriguang

谢谢分享啊 我真的好需要啊

sylar

等图中  呵呵

linda.!

LZ辛苦了，整理的很清晰！强大呀！

bookpig

这样是原创，要好好支持下的。

王晓强

坚持就是胜利~

l16178967

要是现在就有图就更好了，谢谢楼主

fly03238

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