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With CDP compatibility enabled, the device can use LLDP to receive and recognize CDP packets from
Cisco IP phones and respond with CDP packets carrying the voice VLAN ID of the device for the IP
phones to configure the voice VLAN automatically. In this way, voice traffic is confined in the configured
voice VLAN and is thus differentiated from other types of traffic.
Configuration Prerequisites
Before configuring CDP compatibility, make sure that:
z LLDP is enabled globally.
z LLDP is enabled on the port connected to an IP phone and is configured to operate in TxRx mode
on the port.
Configuring CDP Compatibility
CDP-compatible LLDP operates in one of the follows two modes:
z TxRx, where CDP packets can be transmitted and received.
z Disable, where CDP packets can neither be transmitted nor be received.
To make CDP-compatible LLDP take effect on certain ports, first enable CDP-compatible LLDP globally
and configure CDP-compatible LLDP to operate in TxRx mode.
Follow these steps to enable LLDP to be compatible with CDP:
To do… Use the command… Remarks
Enter system view
system-view
—
Enable CDP compatibility
globally
lldp compliance cdp
Required
Disabled by default.
Enter Ethernet interface view
interface interface-type
interface-number
Required
Configure CDP-compatible
LLDP to operate in TxRx
mode
lldp compliance admin-status cdp
txrx
Required
By default,
CDP-compatible LLDP
operates in disable mode.
As the maximum TTL allowed by CDP is 255 seconds, ensure that the product of the TTL multiplier and
the LLDPDU transmit interval is less than 255 seconds for CDP-compatible LLDP to work properly with
Cisco IP phones. You can use related commands to configure the TTL multiplier and the LLDPDU
transmit interval. For details, see
Setting Other LLDP Parameters.
Configuring LLDP Trapping
LLDP trapping is used to notify the network management system (NMS) of events such as new
neighboring devices detected and link malfunctions.
To prevent excessive LLDP traps from being sent when topology is unstable, you can set a minimum
trap sending interval for LLDP.
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