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Question 4: あなたが相互に 接続されている 2 つの Cisco ルータで CDP を有効にします。両方のル
ータのインタフェースのためのラインとプロトコルのステータスが UP と表示されますが、
ルータは互いの CDP ネイバーは表示されません。 OSI モデルのどの層は問題が存在する可能
性が最も高いですか?
A. Physical
B. Session
C. Application
D. Data-Link
E. Network
Correct Answer: D
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.
Reference: "Configuring CDP"
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.1E/native/configuration/guide
/c dp.html