How to troubleshoot the VOICE VLAN of the NBS switch not working properly？

1.Fault Phenomenon:
After configuring the Voice VLAN on the NBS switch, voice traffic fails to be transmitted normally or the device fails to join the Voice VLAN.
Key Points:
Is the global Voice VLAN feature enabled?
Is the port mode Trunk mode (required for automatic mode)?
Is the correct OUI (Organizationally Unique Identifier) configured?
Is the Voice VLAN feature and security mode enabled on the port?
Is there a VLAN configuration conflict or has the Voice VLAN not been re-enabled after a port mode switch?
2. Analysis of the Problem Causes：
The possible causes of this issue include:
Port mode error: The automatic mode of Voice VLAN requires the port to be in Trunk mode; otherwise, it will not take effect；
OUI Not Configured: The MAC address prefix (OUI) of the voice device has not been added, causing the switch to be unable to recognize voice traffic.

Security Mode Conflict: After enabling the security mode, non-voice traffic will be discarded, and voice traffic cannot be transmitted if the OUI is not correctly matched.
VLAN Configuration Conflict: The VLANs allowed on the port do not include the Voice VLAN, or the Native VLAN is misconfigured.
Hardware Limitation: Layer 3 ports or aggregated interfaces do not support the Voice VLAN feature.
3. Troubleshooting Steps and Solutions：
Step 1: Check the global Voice VLAN configuration
Path: Project > Device Config> Voice VLAN > Settings
Requirements :
Enable the Voice VLAN feature.
Set the correct VLAN ID (e.g., 5).
The aging time defaults to 1440 minutes (adjustable).
CoS priority is recommended to be set to 6 (to increase the priority of voice traffic).



Step 2: Configure OUI
Path: Project > Device Config> > Voice VLAN > OUI
Operation:
Add the MAC address prefix of the voice device (e.g., 00-1B-63).
If the device supports LLDP, it can automatically learn OUI (the port Voice VLAN function needs to be enabled).



Step 3: Check port configuration
Path: Project > Device Config> Voice VLAN > Port Settings
Key Configuration:
Mode: Automatic mode (requires the port to be in Trunk mode) or Manual mode.
Security Mode: When enabled, only traffic matching the OUI is allowed (recommended to enable).
VLAN Member : Confirm that the VLANs allowed on the port include the Voice VLAN.





Step 4: Verify Port Mode
Path: Project > Device>Device information>Configuration>Interface> Port List
Requirements :
Port mode must beTrunk(required for automatic mode).
If the port mode has been switched (e.g., Access → Trunk), you need to first disable the Voice VLAN and then re-enable it.
Step 5: Confirm whether the cloud configuration has been synchronized to the device， If configured locally, this step can be skipped.



Step 6: Eliminate hardware limitations
Confirm that the port is not a Layer 3 interface or an aggregated interface (Voice VLAN is not supported).
Check if the device model supports Voice VLAN (all NBS series support it).