Configuring Cdp Compatibility; Configuration Prerequisites - 3Com 4500G Family Configuration Manual

To do...
Enter system view
Enter Ethernet
interface view or
port group view
Set the encapsulation format for
LLDPDUs to SNAP
LLDP-CDP (CDP is short for the Cisco Discovery Protocol) packets use only SNAP encapsulation.

Configuring CDP Compatibility

For detailed information about voice VLAN, refer to VLAN Configuration in the Access Volume.
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 to differentiate the voice
traffic from other types of traffic.
By configuring CDP compatibility, you can enable LLDP on your device to receive and recognize CDP
packets from Cisco IP phones and respond with CDP packets carrying the voice VLAN configuration
TLV for the IP phones to configure the voice VLAN automatically. Thus, the voice traffic is confined in
the configured voice VLAN to be differentiated from other types of traffic.

Configuration Prerequisites

Before configuring CDP compatibility, make sure that:
LLDP is enabled globally.
LLDP is enabled on the port connected to an IP phone and is configured to operate in TxRx mode
on the port.
system-view
Enter Ethernet
interface interface-type
interface view interface-number
Enter port port-group manual
group view port-group-name
lldp encapsulation snap
Use the command...
1-11
Remarks
—
Required
Use either command.
Required
Ethernet II encapsulation
format applies by default.
To restore the default, use
the undo lldp
encapsulation command.