关于NP832中，CDP排错那题的疑问。请教各位大侠！

GSmajia

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题库给出的答案：
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以上的答案解释我不完全认可，我认为interface up代表是物理接口没有问题，而line protocol up应该表示数据链路层也没问题。
不知我的理解对不对？请教各位大侠！

aleser

木有图

GSmajia

图片上传好像有问题。
现我把题目和答案都贴出来，请各位大侠指导。
QUESTION NO: 7
You enabled CDP on two Cisco Routers which are connected to each other. The Line and
Protocol status for the interfaces on both routers show as UP but the routers do not see
each other a CDP neighbors. Which layer of the OSI model does the problem most likely
exist?
A. Physical
B. Session
C. Application
D. Data-Link
E. Network
Answer: D

题库给出的答案的解释：
Explanation:
CDP is a protocol that runs over Layer 2 (the data link layer) on all Cisco routers, bridges, access
servers, and switches. CDP allows network management applications to discover Cisco devices
that are neighbors of already known devices, in particular, neighbors running lower-layer,
transparent protocols. With CDP, network management applications can learn the device type and the SNMP agent address of neighboring devices. This feature enables applications to send SNMP
queries to neighboring devices. In this case, the line protocol is up which means that the physical
layer is operational (layer 1) but the data link layer is not.

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以上的答案解释我不完全认可，我认为interface up代表是物理接口没有问题，而line protocol up应该表示数据链路层也没问题。
不知我的理解对不对？请教各位大侠！

若隐若现

拿分走人呵呵，楼下继续！