[单选题]当在一个接口上使用ipaccess-group99in命令时，以下哪条关于所引用访问控制列表的描述是正确的（）

正确答案 ：C

这个列表是编号型标准ACL，检查进入接口的数据包

[单选题]A Ezonexam technician is troubleshooting connectivity problems between two routers that are directly connected through the serial line. The technician notices that the serial line is up but cannot see any neighbors displayed in the output of the show cdp neighbors command.In which OSI layer is the problem most likely occurring?

正确答案 ：B

Data link

解析：解析：Explanation:Asthequestionstatesthatseriallineisup,itmeanstheproblemisnotontheNetworklayer.Theadministratorcannotseeanyoutputbyissuingtheshowcdpneighborscommand.ItmeansthatCDPisdisabledandCDPisaprotocolthatrunsoverLayer2(thedatalinklayer)onallCiscorouters,bridges,accessservers,andswitches.

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