H3C Technologies H3C S3600 Series Switches - Manual (Page 1158)

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On a S3600 series switch, only one voice VLAN exists at any given point in time. For detailed
information about voice VLAN, refer to Voice VLAN Operation in this manual.
You need to enable CDP compatibility for your device to work with Cisco IP phones.
As your LLDP-enabled device cannot recognize CDP packets, it does not respond to the requests of
Cisco IP phones for the voice VLAN ID configured on the device. This can cause a requesting Cisco IP
phone to send voice traffic without any tag to your device, disabling your device from differentiating
voice traffic from other types of traffic.
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.