v103新题疑问

wgzmk

64. In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?

A. during high traffic periods

B. after broken links are re-established

C. when upper-layer protocols require high reliability

D. in an improperly implemented redundant topology

E. when a dual ring topology is in use

一种新型基于双环形拓扑结构的低相干光纤干涉仪,

Answer: D在一个LAN中有若干的单播帧的拷贝。在一般来说我们的每个单播帧都是只有一个目的地，从而从一个相关接口发送出去就可。如果有若干个单播帧的拷贝就表示我的交换机上同这个目的地址绑定的接口有多个，而这些都应该是不必要的。因为我到一个目的地从一条路走就可以了，如果出现了多条路，那么就应该是做冗余的，可是不正确的冗余配置可能导致我的LAN中产生环路，从而形成在LAN中有同一个帧的多个拷贝。

51cto网

Which two of these are characteristics of the 802.1Q protocol?(choose two)

A. it is a layer 2 messaging protocol which maintains vlan configurations across network.

B. it includes an 8-bit field which specifies the priority of a frame.

C. it is used exclusively for tagging vlan frames and dose not address network reconvergence following switched network topology changes.

D. it modifies the 802.3 frame header,and thus requires that the FCS be recomputed（重计算）.

E. it is a trunking protocol capable of carring untagged frames.

Answer: CD。我刚搜的。A？？

yrb

Which two of these are characteristics of the 802.1Q protocol?(choose two)
这题选：ＤＥ