CDP and LLDP are both discovery protocols used to find information about first hop neighbor network devices.

The Cisco Discovery Protocol (CDP) is a proprietary Data Link Layer protocol developed by Cisco Systems. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address.

CDP (Cisco Discovery Protocol) characteristics:

The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbours on an IEEE 802 local area network, principally wired Ethernet.

LLDP (Link ayer Discovery Protocol) characteristics:

Configuration

CDP configuration commands:

Switch# config terminal
!--- Disable CDP on interface
Switch(config)# no cdp run
!--- Enable CDP on interface
Switch(config)# cdp run
!---
Switch(config)# interface TenGigabitEthernet4/1
!--- Disable CDP on interface
Switch(config-if)# no cdp enable
!--- Enabled CDP on interface
Switch(config-if)# cdp enable

To see information about neighbors via CDP use following commands:

Switch#show cdp neighbours
!
Switch#show cdp neighbours detail
!
Switch#show cdp entry
!
Switch#show cdp interface

LLDP configuration commands:

Switch#configure terminal

!--- Enable LLDP globally on the switch.
Switch(config)#lldp run

!--- Specify time for the device to hold LLDP information.
Switch(config)#lldp holdtime 180

!--- Set the time for sending frequency of LLDP updates.
Switch(config)#lldp timer 50

!--- Enable LLDP specific to an interface.
Switch(config)#interface gigabitethernet 1/0/1

!--- Enable the interface to send LLDP.
Switch(config-if)#lldp transmit

!--- Enable the interface to receive LLDP.
Switch(config-if)#lldp receive

To see information about neighbours via LLDP use following commands:

show lldp neigbours

show lldp neigbours detail

To show LLDP counters use:

show lldp traffic

To see LLDP issues:

show lldp errors

Note: Remember to save configuration after making changes otherwise new configuration will be lost after device restart . To do it use “write memory” command.

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