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CDP / LLDPPrivileged EXEC

show lldp neighbors detail

Displays detailed information about LLDP neighbors, including device capabilities, management addresses, and port descriptions, used for verifying Layer 2 topology and device discovery.

Syntax·Privileged EXEC
show lldp neighbors detail

When to Use This Command

  • Verify that a newly connected switch is properly advertising its capabilities and management IP address.
  • Troubleshoot a missing or incomplete neighbor entry to identify LLDP misconfiguration or incompatible settings.
  • Document the physical topology by collecting detailed neighbor information from multiple devices.
  • Check the remote device's software version and platform to confirm compatibility before integration.

Command Examples

Basic LLDP neighbor detail output

show lldp neighbors detail
------------------------------------------------
Local Intf: Gi0/0
Chassis id: 0011.2233.4455
Port id: Gi0/1
Port Description: GigabitEthernet0/1
System Name: Switch-A
System Description: Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 15.2(2)E7, RELEASE SOFTWARE (fc3)
Time remaining: 112 seconds
System Capabilities: B, R
Enabled Capabilities: B, R
Management Addresses:
  IP: 192.168.1.10
Auto Negotiation - supported, enabled
Physical media capabilities:
  1000baseT(FD)
  100base-TX(FD)
  100base-TX(HD)
  10base-T(FD)
  10base-T(HD)
Media Attachment Unit type: 16
Vlan ID: 10
------------------------------------------------

Local Intf: The local interface on which the LLDP frame was received. Chassis id: The MAC address of the remote device. Port id: The remote interface. Port Description: Description of the remote port. System Name: Hostname of the neighbor. System Description: Full software and hardware description. Time remaining: Seconds until the LLDP entry expires. System Capabilities: Advertised capabilities (B=Bridge, R=Router). Enabled Capabilities: Currently active capabilities. Management Addresses: IP addresses used for management. Auto Negotiation: Shows if autonegotiation is supported and enabled. Physical media capabilities: Supported media types. Media Attachment Unit type: MAU type code. Vlan ID: VLAN associated with the port.

LLDP neighbor detail with multiple management addresses

show lldp neighbors detail
------------------------------------------------
Local Intf: Gi0/1
Chassis id: 0022.3344.5566
Port id: Gi0/2
Port Description: Link to Core
System Name: Core-Router
System Description: Cisco IOS XR Software, Version 6.2.1
Time remaining: 95 seconds
System Capabilities: R
Enabled Capabilities: R
Management Addresses:
  IP: 10.0.0.1 (IPv4)
  IP: 2001:db8::1 (IPv6)
Auto Negotiation - supported, enabled
Physical media capabilities:
  1000baseT(FD)
  100base-TX(FD)
Media Attachment Unit type: 16
Vlan ID: 100
------------------------------------------------

This example shows a router neighbor with both IPv4 and IPv6 management addresses. The System Capabilities indicate only Router (R). The Vlan ID is 100, indicating the port is in VLAN 100. The Port Description 'Link to Core' helps identify the purpose of the link.

Understanding the Output

The output of 'show lldp neighbors detail' provides a comprehensive view of each LLDP neighbor. The 'Local Intf' field identifies which local interface received the LLDP advertisement. 'Chassis id' is typically the MAC address of the remote device, uniquely identifying it. 'Port id' is the remote interface name. 'Port Description' is a human-readable description configured on the remote port. 'System Name' is the hostname of the neighbor. 'System Description' includes the exact IOS version and platform, useful for inventory and compatibility checks. 'Time remaining' indicates how long before the entry is aged out (default TTL is 120 seconds). 'System Capabilities' and 'Enabled Capabilities' use letters: R for Router, B for Bridge (switch), T for Telephone, W for WLAN Access Point, etc. 'Management Addresses' lists IP addresses used for SNMP or telnet/SSH management; multiple addresses may appear. 'Auto Negotiation' and 'Physical media capabilities' show the supported and negotiated speeds/duplex. 'Media Attachment Unit type' is a code for the physical interface type. 'Vlan ID' shows the VLAN configured on the remote port. In a real network, look for mismatched capabilities (e.g., a switch not showing Bridge capability) or missing management addresses, which could indicate configuration issues. Also, verify that the 'System Name' matches your naming conventions and that the 'Port Description' is meaningful for troubleshooting.

CCNA Exam Tips

1.

CCNA exam tip: LLDP is a vendor-neutral protocol; know that it is disabled by default on Cisco devices and must be enabled globally with 'lldp run'.

2.

CCNA exam tip: The 'show lldp neighbors detail' command is used to verify the remote device's management IP address, which is critical for remote management.

3.

CCNA exam tip: Be able to identify the 'System Capabilities' field; for example, a switch will show 'B' (Bridge) and a router will show 'R' (Router).

4.

CCNA exam tip: The 'Time remaining' field indicates the TTL; if it is consistently low, the neighbor may be flapping or the LLDP timer is misconfigured.

Common Mistakes

Mistake 1: Forgetting to enable LLDP globally with 'lldp run' before using 'show lldp neighbors detail' — the command will show no neighbors.

Mistake 2: Confusing LLDP with CDP; LLDP is IEEE standard, CDP is Cisco proprietary. Both serve similar purposes but have different commands.

Mistake 3: Assuming that 'show lldp neighbors detail' shows all neighbors; it only shows neighbors that have sent LLDP advertisements and are in the LLDP database.

Related Commands

show cdp neighbors detail

Displays detailed information about directly connected Cisco devices discovered via CDP, including IP addresses, IOS version, platform, and interface details, useful for verifying neighbor relationships and troubleshooting Layer 2 connectivity.

show lldp neighbors

Displays information about directly connected LLDP-capable devices, including device ID, local interface, hold time, capability, and port ID, used to verify LLDP neighbor discovery and troubleshoot Layer 2 connectivity.

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