In which configuration mode is show lldp neighbors detail used?

The show lldp neighbors detail command is entered in Privileged EXEC mode on Cisco IOS devices.

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.

Definition: show lldp neighbors detail is a Cisco IOS privileged exec command. Displays detailed information about LLDP neighbors, including device capabilities, management addresses, and port descriptions, used for verifying Layer 2 topology and device discovery.

Overview

The `show lldp neighbors detail` command is a powerful diagnostic tool in Cisco IOS that provides an exhaustive view of all LLDP (Link Layer Discovery Protocol) neighbors discovered on a device. LLDP is an IEEE 802.1AB standard protocol that allows network devices to advertise their identity, capabilities, and neighbors on an Ethernet network. This command is essential for verifying Layer 2 topology, ensuring proper device discovery, and troubleshooting connectivity issues at the data link layer.

Unlike CDP (Cisco Discovery Protocol), which is Cisco proprietary, LLDP is vendor-neutral, making it critical in multi-vendor environments. Network engineers reach for this command when they need to confirm that LLDP is functioning correctly, identify neighboring devices, check their capabilities (e.g., router, switch, bridge), and obtain management IP addresses for remote access. It is often used during initial network deployment, after configuration changes, or when troubleshooting connectivity problems that may stem from misconfigured LLDP settings.

The command outputs detailed information for each neighbor, including chassis ID, port ID, system name, system description, port description, supported capabilities, enabled capabilities, management addresses, and more. This data is invaluable for building an accurate network map and ensuring that devices can communicate effectively. In the broader workflow, `show lldp neighbors detail` is typically used after enabling LLDP globally and on interfaces, and before performing more advanced troubleshooting with tools like ping, traceroute, or SNMP.

It is also useful for verifying that LLDP timers and TLVs (Type-Length-Values) are configured correctly. Important IOS behavior to note: the output can be lengthy, especially in large networks with many neighbors, so it may be buffered or truncated if the terminal length is not set appropriately (use `terminal length 0` to disable paging). The command requires privileged EXEC mode (enable) and does not modify the running configuration.

It is also worth noting that LLDP must be enabled globally with `lldp run` and on specific interfaces with `lldp enable`; otherwise, the command will return no neighbors. Understanding this command is fundamental for CCNA and CCNP candidates as it reinforces concepts of Layer 2 discovery protocols and network documentation.

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.

Configuration Scenarios

Verify LLDP Neighbors on a Switch in a Multi-Vendor Network

A network administrator has a Cisco switch connected to a Juniper router and needs to confirm that LLDP is working correctly to discover the router. This scenario demonstrates how to use the command to verify neighbor details.

Topology

SW1(Gi0/1)---10.0.0.0/24---(Ge0/0)Juniper-Router

Steps

1.Step 1: Enter privileged EXEC mode on SW1: SW1> enable
2.Step 2: Display detailed LLDP neighbor information: SW1# show lldp neighbors detail
3.Step 3: Review the output for the Juniper router's details, including system name, management IP, and capabilities.

Configuration

! No configuration needed for verification; ensure LLDP is enabled globally and on interfaces.
SW1(config)# lldp run
SW1(config)# interface GigabitEthernet0/1
SW1(config-if)# lldp enable

Verify: Expected output includes a section for each neighbor. For the Juniper router, look for: System Name: 'Juniper-Router', System Description: 'Juniper Networks, Inc. ...', Management Addresses: '10.0.0.1', Capabilities: 'Router'.

Watch out: If LLDP is not enabled on the interface, the neighbor will not appear. Also, ensure that the neighbor device supports LLDP and has it enabled.

Troubleshoot Missing LLDP Neighbor on a Cisco Switch

A network engineer notices that a newly connected Cisco switch is not appearing in the LLDP neighbor table of an upstream switch. This scenario uses the command to diagnose the issue.

Topology

Upstream-SW(Gi0/2)---192.168.1.0/30---(Gi0/1)New-SW

Steps

1.Step 1: On Upstream-SW, check if LLDP is enabled globally: Upstream-SW# show lldp
2.Step 2: Verify LLDP is enabled on the interface: Upstream-SW# show lldp interface GigabitEthernet0/2
3.Step 3: Check for any neighbors: Upstream-SW# show lldp neighbors
4.Step 4: If no neighbors, run detailed command to see if any partial info exists: Upstream-SW# show lldp neighbors detail
5.Step 5: On New-SW, ensure LLDP is enabled globally and on its interface: New-SW(config)# lldp run; interface Gi0/1; lldp enable

Configuration

! On Upstream-SW:
Upstream-SW(config)# lldp run
Upstream-SW(config)# interface GigabitEthernet0/2
Upstream-SW(config-if)# lldp enable
! On New-SW:
New-SW(config)# lldp run
New-SW(config)# interface GigabitEthernet0/1
New-SW(config-if)# lldp enable

Verify: After enabling LLDP on both sides, the command `show lldp neighbors detail` on Upstream-SW should display New-SW with its system name, management IP (e.g., 192.168.1.2), and capabilities (Switch).

Watch out: Common mistake: Forgetting to enable LLDP on the interface even if it is enabled globally. Also, check for interface errors or VLAN mismatches that could prevent LLDP frames from being exchanged.

Troubleshooting with This Command

When using `show lldp neighbors detail` for troubleshooting, the first step is to understand what healthy output looks like. A healthy output will list each neighbor with a complete set of fields: Chassis ID (typically the MAC address), Port ID (interface name), System Name (hostname), System Description (hardware/software version), Port Description (administrative description), Capabilities (e.g., Router, Switch, Bridge), Management Address (IP address for SNMP or Telnet/SSH), and TTL (time-to-live). Problem indicators include missing neighbors, incomplete fields, or stale entries.

If a neighbor is missing entirely, check if LLDP is enabled globally (`lldp run`) and on the interface (`lldp enable`). Also verify that the neighbor device supports LLDP and has it enabled. If the output shows a neighbor but with 'Management Addresses: not advertised', this may indicate that the neighbor is not configured with an IP address or that LLDP management address TLV is disabled.

Focus on the 'Capabilities' field: if a device is expected to be a router but shows only 'Bridge', it may be misconfigured. Common symptoms this command helps diagnose include: inability to discover network topology, failure to reach a device via its management IP, or unexpected device types. A step-by-step diagnostic flow: 1) Run `show lldp neighbors` to get a summary; if no neighbors, proceed to step 2. 2) Verify LLDP status globally with `show lldp`. 3) Check interface-specific LLDP status with `show lldp interface [interface]`. 4) Ensure the interface is up/up and not in an error-disabled state. 5) Use `debug lldp packets` (with caution) to see if LLDP frames are being sent/received. 6) Correlate with `show cdp neighbors detail` if CDP is also enabled, as both protocols can coexist but may provide different information.

For example, if CDP shows a neighbor but LLDP does not, the issue is likely LLDP-specific. Additionally, check the LLDP timer and hold multiplier with `show lldp`; if the TTL is too short, neighbors may expire prematurely. The output of `show lldp neighbors detail` can also be used to verify that the correct management address is being advertised, which is crucial for network management tools.

If the management address is incorrect, check the interface IP configuration or the `lldp management-address` command. Finally, remember that LLDP is a Layer 2 protocol, so it operates within a broadcast domain; it will not cross routers unless they are configured as transparent bridges. By systematically analyzing the detailed output, network engineers can quickly isolate LLDP-related issues and ensure accurate device discovery.

CCNA Exam Tips

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'.

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.

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).

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.

show lldp neighbors detail vs show lldp neighbors

Both commands display LLDP neighbor information, but 'show lldp neighbors detail' provides extended details such as management addresses and capabilities, while 'show lldp neighbors' gives a concise summary. They are often compared when deciding the level of detail needed for troubleshooting or verification.

Aspect	show lldp neighbors detail	show lldp neighbors
Verbosity	Detailed output per neighbor	One-line summary per neighbor
Key fields shown	Capabilities, management address, port description, system description	Device ID, local interface, hold time, capability, port ID
Use case	Deep dive into neighbor specifics (e.g., verify management IP)	Quick check of connected LLDP neighbors
Output length	Multi-line per neighbor	Single line per neighbor
Typical scenario	Troubleshooting or inventory with detailed info	Initial discovery or when summary suffices

Use show lldp neighbors detail when you need to verify management addresses, capabilities, or port descriptions for deeper troubleshooting or documentation.

Use show lldp neighbors when you want a quick overview of all LLDP neighbors and their basic connectivity status.

Platform Notes

In IOS-XE (e.g., Catalyst 9000 series), the `show lldp neighbors detail` command syntax and output are largely identical to classic IOS, but there may be slight differences in the formatting of the 'System Description' field, which can be more verbose. On NX-OS (e.g., Nexus switches), the equivalent command is `show lldp neighbors detail` as well, but NX-OS uses a different underlying implementation; the output includes additional fields like 'Enabled Capabilities' and 'Port ID TLV'. Additionally, NX-OS requires LLDP to be enabled per VDC (Virtual Device Context).

For ASA firewalls, LLDP is not supported; instead, CDP is used for discovery. In IOS-XR (e.g., ASR 9000), the command is `show lldp neighbors detail` but the output format is distinct, with fields like 'Device ID', 'Interface', 'Port ID', 'Hold Time', and 'Capabilities'. IOS-XR also requires LLDP to be enabled under the 'lldp' configuration mode.

Between IOS versions, the command has remained consistent from 12.x through 16.x, though newer versions may include additional TLVs such as 'Power via MDI' or '802.1 VLAN'. Always check the specific platform documentation for any nuances. For CCNA/CCNP candidates, it is important to know that while the command is similar across platforms, the configuration steps and default states may vary; for example, LLDP is often disabled by default on Cisco switches and must be explicitly enabled.

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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