Cisco Discovery Protocol (CDP)

CDP is a Cisco proprietary Layer 2 protocol that is used for collecting directly connected neighbor device information like hardware, software, device name details and many more…

CDP operation

• Destination address: (multicast) 01-00-0c-cc-cc-cc
• Update timer: (default) 60 sec
• Hold-down timer: (default) 180 sec

Known Issues on CDP

• CDP Can Consume All Router Memory: When a large amount of CDP neighbor announcements are sent, it is possible to consume all memory of an available device. This causes a crash or other abnormal behavior.

Link Layer Discovery Protocol (LLDP)

Link Layer Discovery Protocol (LLDP) is a vendor independent Data Link layer protocol used by network devices for advertising their identity, configuration information, capabilities to neighbors on a LAN segment.

LLDP Operation

• Destination address: (multicast) 01:80:c2:00:00:0e
• Update timer: (default) 30 sec
• Hold-down timer: (default) 120 sec

More Understanding

• Cisco Discovery Protocol (CDP)
• Link Layer Discovery Protocol (LLDP)

References

• Configuring Cisco Discovery Protocol on Cisco Routers and Switches Running Cisco IOS
• Configuring LLDP, LLDP-MED, and Wired Location Service
• CDP & LLDP