正确答案: D

telnet密码未设置

题目：某台PC，能ping通路由器，但不能telnet到路由器，可能的原因是（）

解析：D

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举一反三的答案和解析：

[多选题]The Ezonexam network administrator issues the ping 192.168.2.5 command and successfully tests connectivity to a host that has been newly connected to the network. Which protocols were used during the test? (Choose two)

ARP

ICMP

解析：解析：Explanation:ARPfindsthehardwareaddressofahostfromaknownIPaddress.Here'showitworks:whenIPhasadatagramtosend,itmustinform.aNetworkAccessprotocol,suchasEthernetorTokenRing,ofthedestination'shardwareaddressonthelocalnetwork.(Ithasalreadybeeninformedbyupper-layerprotocolsofthedestination'sIPaddress.)IfIPdoesn'tfindthedestinationhost'shardwareaddressintheARPcache,itusesARPtofindthisinformation.ICMPworksattheNetworklayerandisusedbyIPformanydifferentservices.ICMPisamanagementprotocolandmessagingserviceproviderforIP.ItsmessagesarecarriedasIPdatagrams.RFC1256isanannextoICMP,whichaffordshosts'extendedcapabilityindiscoveringroutestogateways.Periodically,routeradvertisementsareannouncedoverthenetwork,reportingIPaddressesfortherouter'snetworkinterfaces.Hostslistenforthesenetworkinfomercialstoacquirerouteinformation.Aroutersolicitationisarequestforimmediateadvertisementsandmaybesentbyahostwhenitstartsup.

[多选题]下列哪一设备工作时，要用到OSI的七个层（一层到七层）（）

PC

网管机

WEB服务器

解析：ABC