164Setting an encapsulation format for LLDPDUsLLDPDUs can be encapsulated in the following formats: Ethernet II or SNAP frames.• With Ethernet II encapsulation configured, an LLDP port sends LLDPDUs in Ethernet II frames andonly processes incoming, Ethernet II encapsulated LLDPDUs.• With SNAP encapsulation configured, an LLDP port sends LLDPDUs in SNAP frames and onlyprocesses incoming, SNAP encapsulated LLDPDUs.By default, LLDPDUs are encapsulated in Ethernet II frames. If the neighbor devices encapsulate LLDPDUsin SNAP frames, configure the encapsulation format for LLDPDUs as SNAP to guarantee normalcommunication with the neighbors.Follow these steps to set the encapsulation format for LLDPDUs to SNAP:To do… Use the command… RemarksEnter system view system-view —Enter Ethernetinterface viewor port groupviewEnter Layer 2Ethernet interfaceviewinterface interface-typeinterface-number RequiredUse either command.Enter port groupview port-group manual port-group-nameSet the encapsulation format forLLDPDUs to SNAP lldp encapsulation snapRequiredEthernet II encapsulationformat applies by default.NOTE:LLDP-CDP (Cisco Discovery Protocol) packets use only SNAP encapsulation.Configuring CDP compatibilityNOTE:For more information about voice VLAN, 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 CiscoIP phones for the voice VLAN ID configured on the device. As a result, a requesting Cisco IP phone sendsvoice traffic without any tag to your device, disabling your device from differentiating the voice trafficfrom other types of traffic.With CDP compatibility enabled, your device can receive and recognize CDP packets from a Cisco IPphone and respond with CDP packets, which carry the voice VLAN configuration TLVs. According to thevoice VLAN configuration TLVs, the IP phone automatically configures the voice VLAN. The voice trafficis confined in the configured voice VLAN, and differentiated from other types of traffic.
