CCNA: LLDP VS CDP DISCOVERY PROTOCOL UNDERSTANDING & LAB

Cisco Discovery Protocol (CDP):

Overview: A Cisco proprietary network protocol. Information about Cisco devices that are directly connected is shared via it. It is exclusive to Cisco equipment and functions similarly to LLDP. It works over the OSI model's L2 (data link layer). By default, on Cisco hardware, enabled.

Important CDP Features

• Cisco-Specific
• Information Sharing
• Topology Discovery
• Device Management

 Link Layer Discovery Protocol (LLDP)

Overview: On a local network, network devices can advertise their identities, capabilities, and neighbors using LLDP, a vendor-neutral Layer 2 discovery protocol. It runs over the OSI model's L2 (data link layer), as defined by the IEEE 802.1AB standard.

Important LLDP Features

• Vendor-Neutral
• Information Exchange
• Topology Discovery
• Automated Configuration

Note: CDP is Cisco proprietary protocol, CDP is enabled on Cisco
devices by default. No need to enable it. 

Verification Commands 

Switch1#show cdp

Switch1#show cdp neighbors

Switch1#show cdp neighbors detail 

Switch1#show cdp interface 

Change CDP timers to 45 sec and holdtime to 60 sec (this command only supports real ISO Devices)

Siwtch1#config t

Siwtch1(config)#cdp timer 45

Siwtch1(config)#cdp holdtime 60

Verification Commands 

Switch1#show cdp

Disable CDP Globally or on an Interface Basis.

Switch1#config t

Switch1(config)#no cdp run

Switch1(config)#exit

Switch1#

Or

Switch1#config t

Switch1(config)#interface range fa0/1, fa0/2

Switch1(config-if)#no cdp enable

Switch1(config-if)#exit

Switch1(config)#exit

Switch1#

LLDP (Link Layer Discovery Protocol)

Note: The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer

protocol and we need to manually enable it on a network device

Configuration:

Switch1#config t

Switch1(config)#lldp run

Switch1(config)#exit

Switch1#

Verification Commands 

Switch1#show lldp 

Switch1#show lldp neighbors

Switch1#show lldp neighbors detail 

Change LLDP timers to 15 sec and holdtime to 30 sec 

Configuration:

Switch1#config t

Switch1(config)#lldp timer 15

Switch1(config)#lldp holdtime 30

Switch1(config)#exit

Switch1#

Disable LLDP globally or on interface basis.

Switch1#config t

Switch1(config)#no lldp run

Switch1(config)#exit

Switch1#

Or

Switch1#config t

Switch1(config)#interface range fa0/0, fa0/1

Switch1(config-if-range)#no lldp transmit

Switch1(config-if-range)#no lldp receive

Switch1(config-if-range)#exit

Switch1(config)#exit

Switch1#

Important Commands:

sh cdp

sh cdp neighbors

sh cdp neighbors details

sh cdp interface 

sh lldp

sh lldp neighbors

sh lldp neighbors detail

sh lldp interface fa x/x