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Difficulty: HardLayer 2 Discovery Protocols (CDP and LLDP)

A network engineer is auditing Layer 2 discovery protocol operation on a Cisco Catalyst switch connected to multi-vendor wireless access points and VoIP endpoints. The engineer executes the CLI command `show lldp entry AP-Floor2` on switch SW-1 and views the following output:

text
Capability codes:
(R) Router, (B) Bridge, (T) Telephone, (W) WLAN Access Point, (P) Repeater, (O) Other

Local Interface: Gi1/0/12
Chassis id: 0027.0d4f.8e10
Port id: Gi0/1
Port Description: GigabitEthernet0/1
System Name: AP-Floor2
System Description: Autonomous AP Software v15.3
Time remaining: 98 seconds
System Capabilities: B, W
Enabled Capabilities: W
Management Address: 10.1.20.15
Management Address Port VLAN ID (PVID): 20

Which statements accurately interpret the operational state and protocol fields in this command output? (Select TWO.)

  1. The neighbor device is connected to local switch interface GigabitEthernet1/0/12, while GigabitEthernet0/1 identifies the port on the remote neighbor device.Answer
  2. The neighbor device advertises System Capabilities as both a Bridge and a WLAN Access Point, but currently functions with only its WLAN Access Point capability enabled.Answer
  3. C
    The neighbor device is transmitting Cisco proprietary CDP frames because the time remaining counter initialized from a default holdtime of 180 seconds.
  4. D
    Local switch interface GigabitEthernet0/1 has been configured with native VLAN 20 based on the Management Address Port VLAN ID field.

Answer

The correct statements are that GigabitEthernet1/0/12 is the local switch interface while GigabitEthernet0/1 is the remote port ID, and that the neighbor supports Bridge and WLAN Access Point capabilities but operates with only WLAN Access Point enabled.
The output from `show lldp entry` provides Layer 2 neighbor discovery details defined by IEEE 802.1AB. The 'Local Interface' line specifies that switch port GigabitEthernet1/0/12 receives the frames, whereas 'Port id' indicates GigabitEthernet0/1 on the remote device. Additionally, the System Capabilities field shows all capabilities supported by the device hardware (Bridge and WLAN Access Point), while Enabled Capabilities indicates that only WLAN Access Point functionality is actively enabled.

Step-by-Step Solution

1
Analyze interface mapping in LLDP CLI output.
Identify 'Local Interface: Gi1/0/12' as the switch's local receiving port and 'Port id: Gi0/1' as the remote neighbor's transmitting interface.
Layer 2 discovery outputs distinguish between local interfaces and remote neighbor port identifiers to accurately identify physical topology connections.
2
Evaluate system and enabled capabilities codes.
System Capabilities lists 'B, W' (Bridge and WLAN Access Point), while Enabled Capabilities lists 'W'.
LLDP TLVs allow neighbor devices to report both their full hardware features and currently active functional roles.
3
Distinguish LLDP protocol parameters from CDP parameters.
Confirm LLDP operates under IEEE 802.1AB standard with a 120-second default holdtime (30s timer × 4 hold multiplier), contrasting CDP's 180-second default holdtime (60s timer × 3).
Recognizing protocol defaults prevents confusing open-standard LLDP data with Cisco proprietary CDP frames.

Key Concept

Interpretation of IEEE 802.1AB LLDP entry output and TLV field mappings
Estimated Time:2m 0s
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Topics

Layer 2 Discovery Protocols (CDP and LLDP)

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