Voice VLAN assignment modes
A port can be assigned to a voice VLAN automatically or manually.
Automatic mode
Use automatic mode when PCs and IP phones are connected in series to access the network through the device, as shown in Figure 53. Ports on the device transmit both voice traffic and data traffic.
When an IP phone is powered on, it sends out protocol packets. After receiving these protocol packets, the device uses the source MAC address of the protocol packets to match its OUI addresses. If the match succeeds, the system performs the following operations:
Assigns the receiving port of the protocol packets to the voice VLAN.
Issues ACL rules to set the packet precedence.
Starts the voice VLAN aging timer.
The system will remove the port from the voice VLAN if no packet is received from the port before the aging timer expires. The aging timer is also configurable.
If the device reboots, the port is reassigned to the voice VLAN to ensure the correct operation of the existing voice connections. The reassignment occurs automatically without being triggered by voice traffic as long as the voice VLAN operates correctly.
Manual mode
Use manual mode when only IP phones access the network through the device, as shown in Figure 54. In this mode, ports are assigned to a voice VLAN that transmits voice traffic exclusively. No data traffic affects the voice traffic transmission.
You must manually assign the receiving port on the device to a voice VLAN. The device uses the source MAC address of the received voice packets to match its OUI addresses. If the match succeeds, the system issues ACL rules to set the packet precedence.
To remove the port from the voice VLAN, you must manually remove it.
Cooperation of voice VLAN assignment modes and IP phones
Some IP phones send out VLAN-tagged packets, and others send out only untagged packets. For correct packet processing, ports of different link types must meet specific configuration requirements in different voice VLAN assignment modes.
Table 12: Configuration requirements for access/trunk/hybrid ports to support tagged voice traffic
Port link type | Voice VLAN assignment mode | Support for tagged voice traffic | Configuration requirements |
|---|---|---|---|
Access | Automatic | No | N/A |
Manual | No | N/A | |
Trunk | Automatic | Yes | The PVID of the port cannot be the voice VLAN. |
Manual | Yes | The PVID of the port cannot be the voice VLAN. Configure the port to forward the packets from the voice VLAN. | |
Hybrid | Automatic | Yes | The PVID of the port cannot be the voice VLAN. |
Manual | Yes | The PVID of the port cannot be the voice VLAN. Configure the port to forward the packets from the voice VLAN with VLAN tags. |
Table 13: Configuration requirements for access/trunk/hybrid ports to support untagged voice traffic
Port link type | Voice VLAN assignment mode | Support for untagged voice traffic | Configuration requirements |
|---|---|---|---|
Access | Automatic | No | N/A |
Manual | Yes | Configure the voice VLAN as the PVID of the port. | |
Trunk | Automatic | No | N/A |
Manual | Yes | Configure the voice VLAN as the PVID of the port. Configure the port to forward the packets from the voice VLAN. | |
Hybrid | Automatic | No | N/A |
Manual | Yes | Configure the voice VLAN as the PVID of the port. Configure the port to forward the packets from the voice VLAN without VLAN tags. |
If an IP phone sends out tagged voice traffic, and its accessing port is configured with 802.1X authentication, guest VLAN, Auth-Fail VLAN, or critical VLAN, the VLAN ID must be different for the following VLANs:
Voice VLAN.
PVID of the accessing port.
802.1X guest, Auth-Fail, or critical VLAN.
If an IP phone sends out untagged voice traffic, the PVID of the accessing port must be the voice VLAN. As a result, 802.1X authentication is not supported.