Exam 300-135 topic 24 question 5 discussion

Actual exam question from Cisco's 300-135

Question #: 5
Topic #: 24

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

Show Suggested Answer

Suggested Answer: D 🗳️
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.
References:

by yeti1 at Jan. 11, 2020, 8:10 a.m.

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yeti1

5 years, 5 months ago

line/proto up/up means up l1/l2. This means the issues is at application layer. likely cdp disabled globally on a per interface basis.

upvoted 1 times

diegonamaste

5 years, 5 months ago

CDP works on layer 2, then D is correct

upvoted 2 times

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