What is LLDP? Some LLDP basic and useful commands
What is LLDP?
Link Layer Discovery Protocol (LLDP) is a standard network discovery protocol similarly to Cisco Discovery Protocol (CDP) or Nortel Discovery Protocol. It helps network administrator to identify network devices. It allows devices to advertise and discover connected devices and their capabilities. Basically Cisco Discovery Protocol runs on Layer 2 (data link layer) on all Cisco manufactured devices. To support non-Cisco devices and to allow for interoperability between other devices, the switch supports the IEEE 802.1AB Link Layer Discovery Protocol (LLDP). LLDP also runs over the data link layer which allows two systems running different network layer protocols to learn about each other.
Configuring LLDP is pretty much exactly the same as CDP. We just need to change the “cdp” part to “lldp” of the commands. While CDP is enabled by default whereas LLDP is not enabled by default.
Some LLDP Commands:
Verifying LLDP when Disabled:
uccollabing#show lldp
% LLDP is not enabled
Verifying LLDP when Enabled
uccollabing#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
Enabling LLDP : You need to enter the command to enable LLDP
uccollabing(config)#lldp run
Diasable LLDP : You need to enter the below command to disable LLDP.
uccollabing(config)#no lldp run
To see neighbor devices using LLDP, enter the below commands: It will give you details like Device ID, Local Interface, Hold-time, Capability, Port ID etc.
uccollabing#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
Router Fa0/1 120 R Fa0/0
Router Fa0/1 120 R Fa0/0
Total entries displayed: 2
To see a detailed information on lldp, enter the below commands.
uccollabing#show lldp neighbors detail
————————————————
Chassis id: 0001.C916.6501
Port id: Fa0/0
Port Description: FastEthernet0/0
System Name: Router
System Description:
Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 04:52 by pt_team
Time remaining: 90 seconds
System Capabilities: R
Enabled Capabilities: R
Management Addresses – not advertised
Auto Negotiation – supported, enabled
Physical media capabilities:
100baseT(HD)
Media Attachment Unit type: 10
Vlan ID: 1
————————————————
Chassis id: 00E0.B0D6.A101
Port id: Fa0/0
Port Description: FastEthernet0/0
System Name: Router
System Description:
Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 04:52 by pt_team
Time remaining: 90 seconds
System Capabilities: R
Enabled Capabilities: R
Management Addresses – not advertised
Auto Negotiation – supported, enabled
Physical media capabilities:
100baseT(HD)
Media Attachment Unit type: 10
Vlan ID: 1
Total entries displayed: 2
uccollabing#
Hope this helps!
I am working in an IT company and having 10+ years of experience into Cisco IP Telephony and Contact Center. I have worked on products like CUCM, CUC, UCCX, CME/CUE, IM&P, Voice Gateways, VG224, Gatekeepers, Attendant Console, Expressway, Mediasense, Asterisk, Microsoft Teams, Zoom etc. I am not an expert but i keep exploring whenever and wherever i can and share whatever i know. You can visit my LinkedIn profile by clicking on the icon below.
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