[单选题]下列对访问控制列表的描述不正确的是（）。

正确答案 ：D

访问控制列表可以应用于路由更新的过程当中

[单选题]You have a class C network, and you need to design it for 5 usable subnets with each subnet handling a minimum of 18 hosts each. Which of the following network masks should you use?

正确答案 ：D

255.255.255.224

解析：解析：Explanation:ThedefaultsubnetmaskforclassCnetworkis255.255.255.0.Ifonehastocreate5subnets,then3bitsarerequired.With3bitswecancreate8subnets.Theremaining5bitsareusedforHosts.Onecancreate30hostsusing5bitsinhostfield.Thismatcheswiththerequirement.IncorrectAnswers:A,B:ThisisanillegalsubnetmaskforaclassCnetwork,asthethirdoctetcannotbedividedwhenusingaclassCnetwork.C:ThisisthedefaultsubnetmaskforaclassCnetwork.Itprovidesforonenetwork,with254usablehostIPaddresses.E:Thissubnetmaskwillprovidefor14separatenetworkswith14hostseach.Thisdoesnotmeettherequirementofaminimumof18hosts.

[单选题]Which one of the following characteristics is true regarding the use of hubs and switches?

正确答案 ：E

Switches increase the number of collision domains in the network.

解析：解析：Explanation:Switchesincreasesthenumberofcollisionsdomainsinthenetwork.SwitchesthatareconfiguredwithVLANswillreducethesizeofthecollisiondomainsbyincreasingthenumberofcollisiondomainsinanetwork,butmakingthemsmallerthanthatofonebig,flatnetwork.IncorrectAnswers:A.SwitchesarecapableofVLANconfigurations,buthubsarenot.B.Hubsaregenerallytheleastcostlymethodpossibletoconnectmultipledevicestogetherinanetwork.C.Switchesforwardbroadcastsandmulticasts,bydefault,toallportswithinthesameVLAN.Onlyroutersblockallbroadcasttrafficbydefault.D.Switchesandhubscanbeequallyefficientinprocessingframes,intheory.Inpractice,switchesaregenerallymoreefficientastheyusuallyhavemoreCPUandmemoryallocatedtothem,andaregenerallymuchmoreexpensivethanasimplehub.

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