正确答案: B

数据链路层

题目：PPP工作在OSI的哪一层（）

解析：B

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举一反三的答案和解析：

[单选题]What is the purpose of the spanning-tree algorithm in a switched LAN?

To prevent switching loops in networks with redundant switched paths.

解析：解析：Explanation:STPisusedinLANswithredundantpathsorroutestopreventloopsinalayer2switchedorbridgedLAN.IncorrectAnswers:A,B:TheprimarypurposeofSTPistopreventloops,notformonitoringormanagementofswitchesorVLANs.D.VLANsareusedtosegmentaLANintomultiplecollisiondomains,buttheSTPprocessalonedoesnotdothis.E.Routersareusedtopreventroutingloopsatlayer3oftheOSImodel.STPoperatesatlayer2.

[单选题]下列命令中，无法正确执行的是（）

Router(config)show run

[多选题]Why is full-duplex Ethernet superior to its single-duplex counterpart? (Select two answer choices.)

It operates without collisions

It provides faster data transfer

解析：解析：Explanation:

[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.

[多选题]The LAN needs are expanding at the Ezonexam corporate office, which is quickly growing. You are instructed to enlarge the area covered by a single LAN segment on the Ezonexam network.Which of the following are layer 1 devices that you can use? (Choose all that apply.)

A hub

A repeater

解析：解析：Explanation:

[单选题]两个VLAN之间要想通信，应该使用的设备是（）

路由器

[单选题]哪个ACL可允许主机10.220.158.10访问web服务器192.168.3.244()

access-list 101 permit tcp 10.220.158.10 0.0.0.0 host 192.168.3.224 eq 80

[单选题]路由器上，命令“show int s0”的显示结果为：Serial0 is up,line protocol is down出现该结果的可能原因是（）

两端设备协议不一致