H3C Technologies H3C S5120 Series Switches - Manual (Page 135)

1-11
To do… Use the command… Remarks
Enter Layer 2
Ethernet port
view
interface interface-type
interface-number
Enter Ethernet
port 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.
LLDP-CDP (Cisco Discovery Protocol) packets use only SNAP encapsulation.
Configuring CDP Compatibility
For detailed information about voice VLAN, see VLAN Configuration in this manual.
To make your device work with Cisco IP phones, you must enable CDP compatibility.
Because 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, disabling your device from differentiating 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. Thus, the voice
traffic is confined in the configured voice VLAN, and 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 modes:
z TxRx: The CDP packets can be transmitted and received.