H3C Technologies H3C S10500 Series Switches - Manual (Page 239)

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To do… Use the command… Remarks
Enter system view system-view —
Enter Layer 2/Layer
3 Ethernet interface
view
interface interface-type
interface-number
Enter Ethernet
interface view
or port group
view
Enter port group
view
port-group manual port-group-name
Required
Use either command.
Set the encapsulation format for
LLDPDUs to SNAP
lldp encapsulation snap
Required
Ethernet II encapsulation
format applies by default.
NOTE:
LLDP-CDP (Cisco Discovery Protocol) packets use only SNAP encapsulation.
Configuring CDP compatibility
NOTE:
For more information about voice VLANs, see the chapter “Voice VLAN configuration.”
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 the requests of Cisco
IP phones for the voice VLAN ID configured on the device. As a result, a requesting Cisco IP phone sends
voice traffic without any tag to your device, and, as a result, 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 the voice VLAN configuration TLVs. According to the
voice VLAN configuration TLVs, the IP phone automatically configures the voice VLAN. As a result, the
voice traffic is confined in the configured voice VLAN, and differentiated from other types of traffic.
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
CDP-compatible LLDP operates in one of the follows modes:
• TxRx—CDP packets can be transmitted and received.
• Disable—CDP packets cannot be transmitted or received.
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.
Follow these steps to enable LLDP to be compatible with CDP: