H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 191)

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Configuring CDP compatibility
To make your device work with Cisco IP phones, you must enable CDP compatibility.
If your LLDP-enabled device cannot recognize CDP packets, it does not respond to requests from Cisco IP
phones for the voice VLAN ID configured on the device. When a requesting Cisco IP phone sends voice
traffic without any tag to your device, your device cannot differentiate the voice traffic from other types of
traffic.
With CDP compatibility enabled, your device can receive and recognize CDP packets from a Cisco IP
phone and respond with CDP packets, which carry TLVs with voice VLAN configuration. The IP phone
automatically configures the voice VLAN according to the voice VLAN configuration TLVs. As a result,
voice traffic is confined in the configured voice VLAN, and differentiated from other types of traffic.
For more information about voice VLANs, see "Configuring voice VLANs."
Configuration prerequisites
Before you configure CDP compatibility, complete the following tasks:
• Globally enable LLDP.
• Enable LLDP on the port connecting to an IP phone and configure the port to operate in TxRx mode.
Configuring CDP compatibility
IMPORTANT:
The maximum TTL value that CDP allows is 255 seconds. To make CDP-compatible LLDP work properly
with Cisco IP phones, make sure that the product of the TTL multiplier and the LLDPDU transmit interval is
less than 255 seconds.
CDP-compatible LLDP operates in one of the following modes:
• TxRx—CDP packets can be transmitted and received.
• Disable—CDP packets can be neither transmitted nor received.
LLDP traps are sent periodically, and the interval is configurable. To make CDP-compatible LLDP take
effect on specific ports, first enable CDP-compatible LLDP globally, and then configure CDP-compatible
LLDP to operate in TxRx mode.
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.