Configuring the Switch to Advertise Voice VLAN Information to an IP Phone

Context

Generally, IP phones that can send tagged voice packets can obtain voice VLAN information from the switch using a protocol such as LLDP (LLDP is used as an example). LLDP needs to be enabled. When the switch receives an LLDPDU from an IP phone, the switch encapsulates voice VLAN information in the LLDPDU and sends it to the IP phone. The IP phone then sends tagged voice packets.

The switch can encapsulate voice VLAN information into LLDPDUs and send them to connected IP phones. However, IP phones of some vendors send Cisco Discovery Protocol (CDP) packets. You can run the voice-vlan legacy enable command to enable CDP-compatible function so that the switch encapsulates voice VLAN information in CDP packets and sends them to connected IP phones.

Procedure

Configuring the switch to advertise voice VLAN information to an IP phone through LLDP
1. Run system-view
  The system view is displayed.
2. Run lldp enable
  LLDP is enabled globally.
  
  By default, LLDP is enabled globally.
3. Run interface interface-type interface-number
  The interface view is displayed.
4. Run lldp enable
  LLDP is enabled on the interface.
  
  After LLDP is enabled in the system view, all interfaces are enabled with LLDP.
Configuring Cisco Discovery Protocol (CDP)-compatible Voice VLAN function
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. Run voice-vlan legacy enable
  CDP-compatible Voice VLAN function is enabled so that the switch encapsulates voice VLAN information in CDP packets and sends them to the IP phone.
  
  By default, CDP-compatible Voice VLAN function is disabled.