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CDP compatibility enables a switch to use LLDP to perform the following tasks:
•
Receive and recognize the CDP packets from the directly-connected device.
•
Send CDP packets to the directly-connected device.
The packets that the switch sends to the neighboring CDP device carry the device ID, the ID of the port
connecting to the neighboring device, the port IP address, the PVID, and the TTL. The port IP address is
the primary IP address of the VLAN interface in up state. The VLAN interface must have the lowest VLAN
ID among all VLANs permitted on the port. If none of the VLAN interfaces of the permitted VLANs is
assigned an IP address or all VLAN interfaces are down, no port IP address will be advertised.
The CDP neighbor-information-related fields in the output of the
display lldp neighbor-information
command show the CDP neighboring device information that can be recognized by the switch. For more
information about the
display lldp neighbor-information
command, see
Layer 2—LAN Switching
Command Reference
.
Configuration prerequisites
Before you configure CDP compatibility, complete the following tasks:
•
Globally enable LLDP.
•
Enable LLDP on the port connecting to a device supporting CDP.
•
Configure LLDP to operate in TxRx mode on the port.
Configuration procedure
CDP-compatible LLDP operates in one of the following modes:
•
TxRx
—CDP packets can be transmitted and received.
•
Disable
—CDP packets cannot be transmitted or received.
LLDP traps are sent periodically, and the interval is configurable.
To make CDP-compatible LLDP take effect on a port, follow these steps:
1.
Enable CDP-compatible LLDP globally.
2.
Configure CDP-compatible LLDP to operate in TxRx mode on the port.
The maximum TTL value that CDP allows is 255 seconds. To make CDP-compatible LLDP work correctly
with Cisco IP phones, configure the LLDP frame transmission interval to be no more than 1/3 of the TTL
value.
To enable LLDP to be compatible with CDP:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable CDP compatibility
globally.
lldp compliance cdp
By default, CDP compatibility is
disabled globally.
3.
Enter Layer 2/Layer 3 Ethernet
interface view or
management Ethernet
interface view.
interface
interface-type
interface-number
N/A