正确答案: B

Data link

题目：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?

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

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举一反三的答案和解析：

[单选题]IP地址为：192.168.50.70，掩码为：255.255.255.248，则该IP和掩码结合划分子网时，每个子网的容量为（）

6

[多选题]网络中经常使用DDN服务，请选出DDN的优点（）

传输质量高

使用虚电路

专用线路

解析：ADE

[单选题]路由器上“水平分割”的功能是：()

阻止路由环路

[单选题]You need to decide on which trunking method to implement in the Ezonexam network. What is a characteristic of ISL and 802.1q frame. tagging in a switched LAN environment?

They provide inter-switch VLAN communication.

解析：解析：Explanation: A trunk link is the other type of Layer 2 port supported on Cisco switches. When a trunk port is configured, it begins marking frames as they exit the port to indicate which VLAN each frame. is associated with.

[单选题]OSI七层模型中，传输层的数据封装名称为（）

段

[单选题]SMTP工作在OSI哪一层（）

应用层

[单选题]为了禁止网络210.93.105.0ftp到网络223.8.151.0，允许其他信息传输，则能实现该功能的选项是：()

access-list 100 deny tcp 210.93.105.0 0.0.0.255 223.8.151.00.0.0.255 eq ftp access list 100 permit ip any any