下面的問題將幫助你評價在本章中學習到的內容。仔細閱讀所有的選項，因為正確答案可能多於1個。選擇每個問題中所有的正確答案。
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最近合併了公司b，它們位於同一座大樓中，並且所有的計算機足夠接近，可以屬於同一個跳。公司a在所有的節點上使用at m主幹和快速e t h e r n e t公司b使用禁止雙絞線基礎上的令牌環網環境。為什麼公司a和公司b為它們新的合併網路選擇了路由)？
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 (構成路由選擇協定的兩個基本機制是什麼)？
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 (路由選擇表的用途是什麼)？
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 (在不同類型的路由選擇協定路由表中可以發現何種類型的信息)？(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 (路由選擇更新的用途是什麼)？
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) (當網路上的節點向另一個跳3個跳上的節點傳送信息表時，在那個信息表的初始地址中包含了什麼地址)？
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 (路由選擇協定的3個目標是什麼)？
a. accuracy
b. quick holddowns
c. rapid convergence
d. low overhead
8) define convergence (定義收斂)。
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 (為什麼動態路由選擇協定考慮動態)？
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 (什麼是靜態路由)？
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 (當使用靜態路由時，何種類型的網路是最好的)？
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 (什麼是自治系統)？
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 (什麼是默認路由)？
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 (距離向量路由器用何種類型的信息來建立它的路由選擇表)？
a. 呼叫packets
b. second-hand information
c. lsps
d. first-hand information
15) what is the count to infinity problem (什麼是無限計數問題)？
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 (什麼是破壞逆轉)？
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 (什麼是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 (什麼是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中的瞬時更新的目的是什麼)？
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 (管理員如何修改i g r p選擇路由的方法)？
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 (在網段之間進行通信的方法是)：
a. bridging
b. routing
c. switching
d. all of the above
22) routing occurs at which layer (路由發生在哪一層)？
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，路由器選擇的最佳路由具有何種特性)？
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 (當路由器接受到數據包時，它通過檢查什麼而決定接受或拒絕數據包)？
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 (路由選擇算法的低代價通常和什麼相關)？
a. optimal route
b. cpu usage
c. accuracy
d. converg e n c e
27) convergence is not an issue if (收斂並不會成為一個問題，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 (網際協定( i p )路由器選擇)：
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 (靜態路由的ip route配置命令包括下列哪一個參數)？
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 (給定網路的下列連線埠：
網路a→路由器x→路由器y→網路b
接口： 接口： 8 6 . 0 . 0 . 0
x 0 y 0
3 5 . 3 . 3 . 4
並假設a和b網路的網路掩碼為2 5 5 . 0 . 0 . 0，則下面的哪一個代表了配置路由器x從網路a向網路b傳送數據的正確命令)？
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 (靜態路由選擇表可以不經人工干預而在任何時候修改)。
a. true
b. false
32) in a hybrid solution of static and dynamic routing, the nonroutable packets are sent to (在靜態和動態路由的混合解決方案中，不可路由的數據包傳送到)：
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 (路由選擇算法如何實現容錯)？
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 (默認靜態路由器的配置命令ip defa u lt需要下列的哪一個參數)？
a. network mask
b. router interface number
c. subnet id
d. network number
35) in a distance vector routing protocol, aging is set for (在距離向量路由選擇協定中，時 效為什麼設定)？
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 (在距離向量算法中，大型或複雜網路的暫停間隔)：
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 (鏈路狀態協定使用什麼作為度)？
a. hops
b. cost
c. cpu usage
d. network operational time
38) flooding in link-state protocol means what (鏈路狀態協定中的泛洪法意味著什麼)？
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 (對內部網關協定的陳述中，哪一 句是正確的)？
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 (外部網關協定又稱為)：
a. inter-domain
b. areas
c. domains
d. intra-domain
41) routing information protocol (rip) can have maximum of (路由信息協定( r i p )最多可以具有多少個跳計數)？
a. 24 hops
b. 16 hops
c. 12 hops
d. 8 hops
42) how many commands are required to configure a router for rip (為路由器配置r i p需要多少個命令)？
a. four
b. three
c. two
d. one
43) rip authentication command can be used with which version of rip (rip鑑別可以和r i p的哪個版本一起使用)？
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(在內部網關路由選擇協定中，一個路由在多長時間之後從路由選擇表中刪除)？
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(下面的哪一個用於在內部網關路由協定中計算度？ )
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? (在增強內部路由網關協定中，最多允許多少個跳計數)？
a. 64
b. 224
c. 128
d. 232
e. 256
47) enhanced interior routing gateway protocol uses which of the following (增強內部路由選擇網關協定使用下列的哪一種)？
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。在連線不相似的網路類型時要使用路由器。
2) a，d。組成路由選擇協定的兩個機制是選擇最佳路由和傳輸數據。
3) c。路由選擇表用來選擇最佳路由。
4) a ，b，d。路由選擇信息表包括目標網路地址和相關的數值，該數值提供了路由準則： 跳、代價度或者下一個路徑。
5) c。路由選擇更新是用來維護路由選擇表的方法。
6) b，c。初始的數據包傳送帶有目標節點和m a c層(路由器的硬體地址)的網路地址的數據包。
7) a，c，d。路由選擇協定的三個目標分別是：準確、快速收斂和低開銷。
8) d。收斂在所有路由器的路由選擇信息表同步時才發生。
9) b。因為路由在互連網路拓撲結構發生變化時將重新計算，所以動態路由協定是動態
10) a。靜態路由是人工輸入到路由選擇表中並且從來不被路由選擇協定更新的。
11) d。只有包含很少的路由器並且不經常改動的小網路適合於靜態路由，這是因為靜態路由在互連網路變動時要根據管理員的要求來更新每個路由器。
12) d。自治系統也可認為是一個區域或者域。它是在較大互連網路中定義的連續路由器集合；儘管它們共享路由選擇信息，但是它們不向區域外傳播信息。
13) d。默認路由通常是靜態類型的路由，它可看作是最後求助的網關，在此所有非路由數據包進行轉發以進一步處理。
14) b。因為距離向量路由器複製它們鄰居的路由選擇表，更新它們並且轉發它們，所以它們使用了第二手信息。
15) a。無限計數問題是第二手信息產生的路由選擇循環。
16) d。破壞逆轉是水平分割的版本，它將“路由不可達”更新傳送迴路由器，從中可學習路由，這樣可避免路由選擇循環。
17) a。r i p是以前的距離向量協定和內部網關協定，它的更新周期是3 0秒，最多1 5個跳計數。
18) d。i g r p是一個距離向量和內部網關協定，最大網路直徑是2 2 4 (即最多2 2 4個跳計數)。
19) c。瞬時更新用來加速收斂。
20) d。管理員可調整用於路由選擇的加權值。
21) d。橋接、路由選擇和交換都可以從一個網段向另一個網段移動通信量。
22) c。路由選擇發生在網路層上。
附錄a 自我測試題答案
23) c。度用來選擇最佳路由。代價和距離在確定最佳路由中可以為一些路由算法用作度尺度。
24) a。路由器通常具有路徑上目標節點的網路地址信息。
25) c。當接收到數據包時，路由器會檢查目標節點的地址。如果路由器不能向目標地址傳送數據包，那么路由器或者扔掉數據包，或者向默認路由器傳送數據包。
26) b。開銷通常和頻寬及c p u使用相關。精度與最佳化的路由有關。
27) d。如果選擇不變的網路拓撲結構為網路總體結構，那么收斂就不是一個問題。答案
a、b和c都表示變化的網路，它們都需要監視收斂。
28) b 。i p路由選擇表允許路由器選擇數據包要採用的下一步路由。
29) c 。ip route命令包括數據包使用的路由器接口的i p地址。它也包括路由指向的網路號和網路的子網掩碼。
30) b。正確的命令是#ip route 86.0.0.0 255.0.0.0 35.3.3.4。答案a通過路由器x的接口向網路a路由通信量。答案c通過路由器x的接口向網路b路由信息量。答案d通過路由器y的接口向網路a路由流量。
31) b。錯。要更改靜態表，需要有授權者的參與。
32) c。在混合類型的網路中，非可路由數據包將路由到指定為最後求助的路由器的靜態路由器中。
33) b。在故障的情況下，分布的路由選擇協定提供了默認容錯技術。
34) d。ip defa u lt命令需要一個網路號。
35) b。距離向量路由選擇算法中的時效設定是針對所有的路由選擇信息。
36) b。對於較大的或複雜的網路，如果停機周期足夠長，那么就會儘可能地減少與網路穩定性有關的問題(儘管不是在所有情況下都適用)。
37) b。作為有關度，連結狀態協定使用代價而不是路程段。
38) c。連結狀態協定中的泛洪就是指連結狀態路由器的鄰居接收到有關連結狀態數據包， 複製該數據包，然後將它轉發到網路中的其餘部分。
39) b. igp在網路內套用到自治系統。
40) a。外部網關協定就是域間協定，因為它們在域間運行。
41) b 。r i p有1 6個路程段的限制。
42) c 。r i p配置需要一個命令來啟用r i p，還需要一個命令來激活r i p接口。
43) b 。r i p鑑別命令僅僅可以和r i p的第2版本一起使用。
44) d。在7個更新周期之後，將從路由選擇表中刪除路由。在i g r p中，每9 0秒更新一次廣播。在三個更新周期之後，此時路由丟失，就是認為路由不可到達。7個周期之後，路由被刪除。
45) e。在i g r p中，互連網路延遲、負載、頻寬和可靠性都用來計算度值。
46) b 。e i g r p中用到的最大跳計數是2 2 4。
47) e。e i g r p將距離向量和d u a l一起使用，這改進了收斂屬性。