题库精选:CCNA考试自测题第2卷
1) company a has recently merged with company b, which exists in the same building and is physically close enough for all the computers to belong on the same network seg ment.
company a uses an atm backbone and fast ethernet for all nodes. company b has a token ring environment on shielded twisted-pair wiring. why will company a and company b select a router for their newly merged network (公司a最近合并了公司b，它们位于同一座大楼中，并且所有的计算机足够接近，可以属于同一个跳。公司a在所有的节点上使用at m主干和快速e t h e r n e t公司b使用屏蔽双绞线基础上的令牌环网环境。为什么公司a和公司b为它们新的合并网络选择了路由)?
a. network segment size has reached the maximum
b. network addresses are not sufficient for a merged network
c. tr a ffic must be segmented to prevent an expected bandwidth overload
d. a router is the usual way to connect dissimilar network types
2) what are the two basic mechanisms that make up a routing protocol (构成路由选择协议的两个基本机制是什么)?
a. route selection
b. flooding
c. autonomous systems
d. data tr a n s m i s s i o n
3) what is a routing table used for (路由选择表的用途是什么)?
a. it is the physical support for the router to sit on
b. it contains a list of all the timers used to prevent routing loops
c. it is used to select the best route
d. it manages the periodic update algorithm
4) what types of information can be found in different types of routing protocol routing tables (在不同类型的路由选择协议路由表中可以发现何种类型的信息)?(select 3)
a. the destination network associated with the next hop
b. the destination network associated with the cost metric
c. the destination network associated with the subnet mask
d. the destination network associated with the next path or interface to use
5) what is a routing update used for (路由选择更新的用途是什么)?
a. routing updates notify neighboring routers with a 呼叫
b. routing updates redistribute routes learned from other routing protocols
c. routing updates maintain the routing table
d. routing updates increase the network addresses available by changing the subnet masks
6) when a node on one network sends a packet to a node on another segment that is three
hops away, what addresses are included in the initial addressing of that packet (select 2) (当网络上的节点向另一个跳3个跳上的节点发送信息表时，在那个信息表的初始地址中包含了什么地址)?
a. the network address of the router
b. the mac layer address of the router
c. the network address of the destination node
d. the mac layer address of the destination node
7) what are three objectives for a routing protocol (路由选择协议的3个目标是什么)?
a. accuracy
b. quick holddowns
c. rapid convergence
d. low overhead
8) define convergence (定义收敛)。
a. convergence is the updates that are triggered by network changes
b. convergence is the process of sending 呼叫packets
c. convergence is two routers merging their routing tables into one
d. convergence is the synchronizing of all routing tables on the internetwork, or simply the synchronization of a single route change across all routers.
9) why are dynamic routing protocols considered dynamic (为什么动态路由选择协议考虑动态)?
a. because each route is dynamically selected for each packet with a destination network not attached to the router。
b. because new routes are dynamically recomputed whenever there is a change in the nternetwork topology
c. because convergence happens faster
d. because all the routes remain the same no matter what changes happen on the network
10) what is a static route (什么是静态路由)?
a. a static route is one that has been manually entered into the routing table and is not updated by a routing protocol
b. a static route is one that is recomputed whenever a change is made on the internetwork
c. a static route is one that is redistributed when it has been learned by another routing protocol
d. a static route is one that comes already configured in the router from the manufacturer
11) what type of network is best when using static routes (当使用静态路由时，何种类型的网络是最好的)?
a. a large network with hundreds of routers and networks
b. a complex internetwork that changes often
c. an autonomous system with multiple connections to other autonomous systems
d. a small network with few routers and infrequent changes
12) what is an autonomous system (什么是自治系统)?
a. an area
b. a domain
c. a contiguous set of routers defined within a larger internetwork, that do not share routing information with the external internetwork
d. all of the above
e. none of the above
13) what is a default route (什么是默认路由)?
a. a type of static route
b. a destination for any nonroutable packet
c. gateway of last resort
d. all of the above
e. none of the above
14) what type of information does a distance vector router build its routing table with (距离向量路由器用何种类型的信息来建立它的路由选择表)?
a. 呼叫packets
b. second-hand information
c. lsps
d. first-hand information
15) what is the count to infinity problem (什么是无限计数问题)?
a. a routing loop that results from the way distance vector protocols use second-hand information
b. the inability of routers to process more than 16 hops
c. the excessive cpu overhead presented by distance vector algorithms
d. the result of using both rip and igrp on the same internetwork
16) what is poison reverse (什么是破坏逆转)?
a. a change to the default update period timer
b. a routing loop that occurs when using second-hand information to update route tables
c. a router virus
d. a version of split-horizon that sends back a “route unreachable” update to the router that the route was learned from, in order to avoid routing loops
17) what is rip (什么是r i p )?
a. rip is an older distance vector interior gateway protocol with a 30-second update timer and . maximum of 15 hops (where “i n f i n i t y” is 16 hops)
b. rip is a new link-state protocol created by cisco
c. rip is a proprietary protocol created by cisco that has two versions; only version 2 is used currently
d. rip is a distance vector interior gateway protocol with a 224 maximum network diameter (maximum 224 hops)
18) what is igrp (什么是i g r p )?
a. igrp is an older distance vector interior gateway protocol with a 30-second update timer and a maximum of 15 hops (where infinity is 16 hops)
b. igrp is a new link-state protocol created by cisco
c. igrp is a proprietary protocol created by cisco that has two versions; only version 2 isused currently
d. igrp is a distance vector and interior gateway protocol with a 224 maximum network diameter (maximum 224 hops)
19) what is the purpose of a flash update in igrp (igrp中的瞬时更新的目的是什么)?
a. a flash update is a standard 90-second update
b. after three flash updates, a route is considered unreachable
c. a flash update is sent immediately upon a change in the network topology, in order to speed convergence
d. after seven flash updates, a route is removed from the routing table
20) how can the administrator change how igrp selects routes (管理员如何修改i g r p选择路由的方法)?
a. the administrator can set update timers
b. the administrator can enable or disable split horizon
c. the administrator can set up load balancing across redundant routes
d. the administrator can adjust the metric weights used for determining the route selection
21) the way to get traffic from one segment of the network to another segment is (在网段之间进行通信的方法是)：
a. bridging
b. routing
c. switching
d. all of the above
22) routing occurs at which layer (路由发生在哪一层)?
a. physical layer
b. data link layer
c. network layer
d. transport layer
23) in general, the bets route selected by a router is one with (一般而言，路由器选择的最佳路由具有何种特性)?
a. least cost
b. shortest distance
c. lowest metric value
d. none of the above
24) a routing table typically includes which of the following (路由表通常包含下列的哪些信息)?
a. destination network address
b. the total number of networks
c. the number of nodes in each network
d. the total number of routers in a network
25) when a router receives a packet, it accepts or rejects a packet by examining what (当路由器接受到数据包时，它通过检查什么而决定接受或拒绝数据包)?
a. the mac address of the source of the packet
b. the address of the source network/node number
c. the address of the destination network/node
d. the mac address of the next router
26) low overhead of a routing algorithm is normally associated with (路由选择算法的低代价通常和什么相关)?
a. optimal route
b. cpu usage
c. accuracy
d. converg e n c e
27) convergence is not an issue if (收敛并不会成为一个问题，如果)：
a. routers are added to the network
b. some of the network interfaces are down
c. cpu/bandwidth usage of the routers changes
d. an invariant network topology is selected for the network architecture
28) an internet protocol (ip) router selects (网际协议( i p )路由器选择)：
a. an entire path from source to destination
b. the next route step
c. the two adjacent routers to itself
d. all of the above.
29) ip route configuration command for a static route includes which of the following parameters (静态路由的ip route配置命令包括下列哪一个参数)?
a. subnetwork number of the destination network
b. subnet mask of the source network
c. ip address of the interface of the router which the packet should use
d. mac address of the next router on the path
30) given the following portion of the network:
network a→ router x→ router y→ network b
i n t e r f a c e : i n t e r f a c e : 8 6 . 0 . 0 . 0
x 0 y0
3 5 . 3 . 3 . 4
and assuming a network mask of 255.0.0.0 for both a and b networks, which one of the
following represents a correct command to configure router x to send data from network a to network b (给定网络的下列端口：
网络a→路由器x→路由器y→网络b
接口： 接口： 8 6 . 0 . 0 . 0
x 0 y 0
3 5 . 3 . 3 . 4
并假设a和b网络的网络掩码为2 5 5 . 0 . 0 . 0，则下面的哪一个代表了配置路由器x从网络a向网络b发送数据的正确命令)?
a. #ip route 85.0.0.0 255.0.0.0 35.3.3.3
b. #ip route 86.0.0.0 255.0.0.0 35.3.3.4
c. #ip route 86.0.0.0 255.0.0.0 35.3.3.3
d. #ip route 85.0.0.0 255.0.0.0 35.3.3.4
31) a static routing table can be changed at any time without manual intervention (静态路由选择表可以不经人工干预而在任何时候修改)。
a. true
b. false
32) in a hybrid solution of static and dynamic routing, the nonroutable packets are sent to (在静态和动态路由的混合解决方案中，不可路由的数据包发送到)：
a. the next router
b. the central router
c. the gateway of last resort
d. the source router where the packets originated
33) how is fault tolerance on a routing algorithm achieved (路由选择算法如何实现容错)?
a. by providing a central control router
b. by a distributed routing protocol
c. by load balancing of the traffic
d. all of the above
34) the configuration command ip defa u lt for a default static router requires which of the following parameters (默认静态路由器的配置命令ip defa u lt需要下列的哪一个参数)?
a. network mask
b. router interface number
c. subnet id
d. network number
35) in a distance vector routing protocol, aging is set for (在距离向量路由选择协议中，时 效为什么设置)?
a. only the next available router
b. all routing information
c. only the unavailable routers
d. only the routers in the lowest metric route
36) in a distance vector algorithm, the holddown interval for large or complex networks (在距离向量算法中，大型或复杂网络的暂停间隔)：
a. cannot be used
b. would need to have a much larger value
c. is equal to negative reachability parameter
d. would need to have a smaller value to reach converg e n c e
37) what do link-state protocols use as a metric (链路状态协议使用什么作为度)?
a. hops
b. cost
c. cpu usage
d. network operational time
38) flooding in link-state protocol means what (链路状态协议中的泛洪法意味着什么)?
a. a router sending all routing information to its neighbors
b. a router broadcasting all information to all routers in the network
c. the neighbors of a link-state router receiving a link-state packet, copying it, and then
forwarding it to the rest of the network
d. a router sending information about the routers that have changed
39) which statement is true of interior gateway protocols (对内部网关协议的陈述中，哪一 句是正确的)?
a. they apply to internet domains
b. they apply to autonomous systems within the network
c. they apply to external networks
d. they allow systems in the internet to manage areas in the network where igp is i m p l e m e n t e d
40) exterior gateway protocols are known as (外部网关协议又称为)：
a. inter-domain
b. areas
c. domains
d. intra-domain
41) routing information protocol (rip) can have maximum of (路由信息协议( r i p )最多可以具有多少个跳计数)?
a. 24 hops
b. 16 hops
c. 12 hops
d. 8 hops
42) how many commands are required to configure a router for rip (为路由器配置r i p需要多少个命令)?
a. four
b. three
c. two
d. one
43) rip authentication command can be used with which version of rip (rip鉴别可以和r i p的哪个版本一起使用)?
a. rip version 1
b. rip version 2
c. rip version 1 and rip version 2
d. none of the above
44) in the interior gateway routing protocol, a route is removed from the routing table after(在内部网关路由选择协议中，一个路由在多长时间之后从路由选择表中删除)?
a. three update periods
b. 60 seconds
c. five update periods
d. seven update periods
e. 90 seconds
45) which of the following is used to calculate metric in interior gateway routing protocol(下面的哪一个用于在内部网关路由协议中计算度? )
a. internetwork delay
b. bandwidth
c. load
d. reliability
e. all of the above
46) what is the maximum allowable number of hops in enhanced interior routing gatewayprotocol? (在增强内部路由网关协议中，最多允许多少个跳计数)?
a. 64
b. 224
c. 128
d. 232
e. 256
47) enhanced interior routing gateway protocol uses which of the following (增强内部路由选择网关协议使用下列的哪一种)?
a. link-state vector
b. diffusion update algorithm
c. distance vector
d. a and b only
e. b and c only
a.5 第5章答案
1) d。在连接不相似的网络类型时要使用路由器。
2) a，d。组成路由选择协议的两个机制是选择最佳路由和传输数据。
3) c。路由选择表用来选择最佳路由。
4) a ，b，d。路由选择信息表包括目标网络地址和相关的数值，该数值提供了路由准则： 跳、代价度或者下一个路径。
5) c。路由选择更新是用来维护路由选择表的方法。
6) b，c。初始的数据包发送带有目标节点和m a c层(路由器的硬件地址)的网络地址的数据包。
7) a，c，d。路由选择协议的三个目标分别是：准确、快速收敛和低开销。
8) d。收敛在所有路由器的路由选择信息表同步时才发生。
9) b。因为路由在互连网络拓扑结构发生变化时将重新计算，所以动态路由协议是动态
10) a。静态路由是人工输入到路由选择表中并且从来不被路由选择协议更新的。
11) d。只有包含很少的路由器并且不经常改动的小网络适合于静态路由，这是因为静态路由在互连网络变动时要根据管理员的要求来更新每个路由器。
12) d。自治系统也可认为是一个区域或者域。它是在较大互连网络中定义的连续路由器集合;尽管它们共享路由选择信息，但是它们不向区域外传播信息。
13) d。默认路由通常是静态类型的路由，它可看作是最后求助的网关，在此所有非路由数据包进行转发以进一步处理。
14) b。因为距离向量路由器复制它们邻居的路由选择表，更新它们并且转发它们，所以它们使用了第二手信息。
15) a。无限计数问题是第二手信息产生的路由选择循环。
16) d。破坏逆转是水平分割的版本，它将“路由不可达”更新发送回路由器，从中可学习路由，这样可避免路由选择循环。
17) a。r i p是以前的距离向量协议和内部网关协议，它的更新周期是3 0秒，最多1 5个跳计数。
18) d。i g r p是一个距离向量和内部网关协议，最大网络直径是2 2 4 (即最多2 2 4个跳计数)。
19) c。瞬时更新用来加速收敛。
20) d。管理员可调整用于路由选择的加权值。
21) d。桥接、路由选择和交换都可以从一个网段向另一个网段移动通信量。
22) c。路由选择发生在网络层上。
附录a 自我测试题答案
23) c。度用来选择最佳路由。代价和距离在确定最佳路由中可以为一些路由算法用作度尺度。
24) a。路由器通常具有路径上目标节点的网络地址信息。
25) c。当接收到数据包时，路由器会检查目标节点的地址。如果路由器不能向目标地址发送数据包，那么路由器或者扔掉数据包，或者向默认路由器发送数据包。
26) b。开销通常和带宽及c p u使用相关。精度与优化的路由有关。
27) d。如果选择不变的网络拓扑结构为网络总体结构，那么收敛就不是一个问题。答案
a、b和c都表示变化的网络，它们都需要监视收敛。
28) b 。i p路由选择表允许路由器选择数据包要采用的下一步路由。
29) c 。ip route命令包括数据包使用的路由器接口的i p地址。它也包括路由指向的网络号和网络的子网掩码。
30) b。正确的命令是#ip route 86.0.0.0 255.0.0.0 35.3.3.4。答案a通过路由器x的接口向网络a路由通信量。答案c通过路由器x的接口向网络b路由信息量。答案d通过路由器y的接口向网络a路由流量。
31) b。错。要更改静态表，需要有授权者的参与。
32) c。在混合类型的网络中，非可路由数据包将路由到指定为最后求助的路由器的静态路由器中。
33) b。在故障的情况下，分布的路由选择协议提供了默认容错技术。
34) d。ip defa u lt命令需要一个网络号。
35) b。距离向量路由选择算法中的时效设置是针对所有的路由选择信息。
36) b。对于较大的或复杂的网络，如果停机周期足够长，那么就会尽可能地减少与网络稳定性有关的问题(尽管不是在所有情况下都适用)。
37) b。作为有关度，链接状态协议使用代价而不是路程段。
38) c。链接状态协议中的泛洪就是指链接状态路由器的邻居接收到有关链接状态数据包， 复制该数据包，然后将它转发到网络中的其余部分。
39) b. igp在网络内应用到自治系统。
40) a。外部网关协议就是域间协议，因为它们在域间运行。
41) b 。r i p有1 6个路程段的限制。
42) c 。r i p配置需要一个命令来启用r i p，还需要一个命令来激活r i p接口。
43) b 。r i p鉴别命令仅仅可以和r i p的第2版本一起使用。
44) d。在7个更新周期之后，将从路由选择表中删除路由。在i g r p中，每9 0秒更新一次广播。在三个更新周期之后，此时路由丢失，就是认为路由不可到达。7个周期之后，路由被删除。
45) e。在i g r p中，互连网络延迟、负载、带宽和可靠性都用来计算度值。
46) b 。e i g r p中用到的最大跳计数是2 2 4。
47) e。e i g r p将距离向量和d u a l一起使用，这改进了收敛属性。
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