CDP / LLDPPrivileged EXEC

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.

Syntax·Privileged EXEC

show lldp neighbors

When to Use This Command

Verify that LLDP is enabled and discovering neighboring Cisco or third-party devices on a network segment.
Troubleshoot missing or incorrect neighbor information when devices are not appearing in the LLDP table.
Identify the remote device type and capabilities (e.g., router, switch, bridge) connected to a specific local interface.
Check the hold time to determine if neighbor entries are aging out prematurely due to network issues.

Command Examples

Basic LLDP Neighbor Display

show lldp neighbors

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

Device ID           Local Intf     Hold-time  Capability      Port ID
Switch-A            Gi0/0          120        B               Gi0/1
Router-B            Gi0/1          90         R               Gi0/0
Phone-C             Gi0/2          60         T               Port 1

Line 1-2: Capability codes legend explaining the letters used in the Capability column. Line 3: Blank line. Line 4: Column headers: Device ID (hostname of neighbor), Local Intf (local interface where neighbor is heard), Hold-time (remaining seconds before entry expires), Capability (device type using codes), Port ID (remote interface of neighbor). Line 5: Switch-A is a Bridge (B) connected to local Gi0/0, with 120 seconds hold time, remote port Gi0/1. Line 6: Router-B is a Router (R) on local Gi0/1, hold time 90 seconds, remote port Gi0/0. Line 7: Phone-C is a Telephone (T) on local Gi0/2, hold time 60 seconds, remote port Port 1.

Detailed LLDP Neighbor with Interface

show lldp neighbors GigabitEthernet0/1 detail

Local Intf: Gi0/1
Chassis id: 0011.2233.4455
Port id: Gi0/0
Port Description: GigabitEthernet0/0
System Name: Router-B
System Description: Cisco IOS Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.7(3)M, RELEASE SOFTWARE (fc2)
Time remaining: 87 seconds
System Capabilities: Router
Enabled Capabilities: Router
Management Addresses:
    IP: 192.168.1.1
Auto Negotiation - supported, enabled
Physical media capabilities:
    1000baseT(FD)
    100baseT(FD)
    100baseT(HD)
    10baseT(FD)
    10baseT(HD)
Media Attachment Unit type: 16
Vlan id: 1

Local Intf: The local interface on which the LLDP frame was received. Chassis id: MAC address of the neighbor device. Port id: Remote interface identifier. Port Description: Description of the remote interface. System Name: Hostname of the neighbor. System Description: Full software version and platform of the neighbor. Time remaining: Seconds until this entry is removed from the LLDP table. System Capabilities: All capabilities the device supports. Enabled Capabilities: Capabilities currently active. Management Addresses: IP addresses used for SNMP or other management. Auto Negotiation: Whether auto-negotiation is supported and enabled. Physical media capabilities: Supported media types and speeds. Media Attachment Unit type: MAU type code. Vlan id: The native VLAN of the interface.

Understanding the Output

The 'show lldp neighbors' command output lists all LLDP neighbors discovered on the device. The first section shows capability codes that map letters to device types (R=Router, B=Bridge, T=Telephone, etc.). The main table has five columns: Device ID (the hostname of the neighbor), Local Intf (the local interface where the neighbor is heard), Hold-time (the remaining time in seconds before the entry expires; a value near 0 indicates the neighbor may be unreachable), Capability (one or more letters indicating device type), and Port ID (the remote interface identifier). A healthy network should show neighbors with hold times typically between 60-120 seconds (default TTL is 120 seconds). If hold times are consistently low or entries disappear, check LLDP timers or connectivity. The detailed version (with 'detail' keyword) provides additional information such as chassis ID, system description, management addresses, and VLAN ID, which is useful for verifying device identity and configuration.

CCNA Exam Tips

Remember that LLDP is a vendor-neutral protocol (IEEE 802.1AB), unlike CDP which is Cisco proprietary; CCNA may ask which protocol to use in a multivendor environment.

The default LLDP hold time multiplier is 4, and the default transmit interval is 30 seconds, resulting in a TTL of 120 seconds; know these values for timer-related questions.

LLDP must be enabled globally with 'lldp run' and per interface with 'lldp transmit' and 'lldp receive'; the exam may test that both are needed for full operation.

The 'Capability' column uses single-letter codes; be able to identify that 'B' stands for Bridge (switch) and 'R' for Router.

Common Mistakes

Forgetting to enable LLDP globally with 'lldp run' before expecting neighbors to appear; the command will show no output if LLDP is disabled.

Confusing LLDP with CDP; both have similar commands but different protocols — CDP uses 'show cdp neighbors' and is Cisco-only.

Assuming that enabling LLDP on one interface is enough; both 'lldp transmit' and 'lldp receive' must be enabled on the interface for two-way discovery.

Related Commands

show cdp neighbors

Displays information about directly connected Cisco devices discovered via CDP, used to verify neighbor relationships and gather device details.

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.

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