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Difficulty: MediumLayer 2 Discovery Protocols (CDP and LLDP)

A network administrator executes a command on a Cisco Catalyst switch to inspect details about a newly connected neighbor switch running Link Layer Discovery Protocol (LLDP). The command produces the following output:

text
Switch-Core# show lldp entry Switch-Access-01

Capability codes:
(R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
(W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

-----------------------------------------------
Local Interface: Gi1/0/12
Chassis id: 0026.98a1.4b80
Port id: Gi0/1
Port Description: GigabitEthernet0/1
System Name: Switch-Access-01

System Description:
Cisco IOS Software, C3750E Software (C3750E-UNIVERSALK9-M), Version 15.0(2)SE11, RELEASE SOFTWARE (fc3)

Time remaining: 92 seconds
System Capabilities: B, R
Enabled Capabilities: B

Management Addresses:
IP: 192.168.10.5

Based on the output above, which statement accurately describes the connected neighbor device and interface topology?

  1. The neighbor device is connected to local port GigabitEthernet1/0/12 and is operating with Bridge capabilities enabled.Answer
  2. B
    The neighbor device is physically attached to local interface GigabitEthernet0/1 and has Router capabilities enabled.
  3. C
    The local switch sends LLDP advertisement updates to the neighbor every 92 seconds by default.
  4. D
    The LLDP system description TLV signals an active native VLAN mismatch on local interface GigabitEthernet1/0/12.

Answer

The neighbor device is connected to local port GigabitEthernet1/0/12 and is operating with Bridge capabilities enabled.
The output explicitly shows 'Local Interface: Gi1/0/12' as the local switch port and 'Enabled Capabilities: B' as the active bridging capability of the connected neighbor Switch-Access-01.

Step-by-Step Solution

1
Identify the local switch interface from the CLI output
The field 'Local Interface: Gi1/0/12' shows that the cable from the neighbor connects directly into port GigabitEthernet1/0/12 on the local switch.
LLDP output explicitly distinguishes between the local receiving interface and the remote neighbor's transmitting port ID.
2
Examine the capabilities fields for the neighbor device
'System Capabilities: B, R' indicates the device supports both Bridge and Router functions, but 'Enabled Capabilities: B' shows only Bridge capability is active.
System capabilities indicate full hardware/software support, whereas enabled capabilities reflect current operational role.
3
Verify holdtime vs transmit frequency definitions
'Time remaining: 92 seconds' is the remaining holdtime before the entry expires if no further LLDP updates arrive (default holdtime is 120 seconds, calculated as 30s retransmit x 4 holdtime multiplier).
The time remaining field counts down from the holdtime timer, not the transmission interval.

Key Concept

Interpreting LLDP Neighbor Details and Capabilities
Estimated Time:1m 15s
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Topics

Layer 2 Discovery Protocols (CDP and LLDP)

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