Device Discovery with LLDP

Posted: 10th October 2021 by ccna7guru in ENSA
Tags: , ,

LLDP Overview

Link Layer Discovery Protocol (LLDP) is a vendor-neutral neighbor discovery protocol similar to CDP. LLDP works with network devices, such as routers, switches, and wireless LAN access points. This protocol advertises its identity and capabilities to other devices and receives the information from a physically-connected Layer 2 device.

Device Discovery with LLDP

Configure and Verify LLDP

•LLDP may be enabled by default. To enable LLDP globally on a Cisco network device, enter the lldp run command in the global config mode. To disable LLDP, enter the no lldp run command in the global config mode.
•LLDP can be configured on specific interfaces. However, LLDP must be configured separately to transmit and receive LLDP packets.
•To verify LLDP is enabled, enter the show lldp command in privileged EXEC mode.

Switch# conf t

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# lldp run

Switch(config)# interface gigabitethernet 0/1

Switch(config-if)# lldp transmit

Switch(config-if)# lldp receive

Switch(config-if)# end

Switch# show lldp

Global LLDP Information:

   Status: ACTIVE

   LLDP advertisements are sent every 30 seconds

   LLDP hold time advertised is 120 seconds

   LLDP interface reinitialisation delay is 2 seconds

Discover Devices by Using LLDP

With LLDP enabled, device neighbors can be discovered by using the show lldp neighbors command.

S1# 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

R1   Fa0/5   117   R   Gi0/0/1

S2   Fa0/1   112   B   Fa0/1

Total entries displayed: 2

When more details about the neighbors are needed, the show lldp neighbors detail command can provide information, such as the neighbor IOS version, IP address, and device capability.

S1# show lldp neighbors detail


Chassis id: 848a.8d44.49b0

Port id: Gi0/0/1

Port Description: GigabitEthernet0/0/1

System Name: R1

System Description: Cisco IOS Software [Fuji], ISR Software (X86_64_LINUX_…..,


Technical Support:

Copyright (c) 1986-2019 by Cisco Systems, Inc.

Compiled Thu 22-Aug-19 18:09 by mcpre

Time remaining: 111 seconds

System Capabilities: B,R

Enabled Capabilities: R

Management Addresses – not advertised

(output omitted)