Security mode and normal mode of voice VLANs
Depending on their inbound packet filtering mechanisms, voice VLAN-enabled ports operate in the
following modes.
• Normal mode: Voice VLAN-enabled ports receive packets carrying the voice VLAN tag, and
forward packets in the voice VLAN without comparing their source MAC addresses against the OUI
addresses configured for the device. If the PVID of the port is the voice VLAN and the port works in
manual VLAN assignment mode, the port forwards all received untagged packets in the voice
VLAN. In normal mode, voice VLANs are vulnerable to traffic attacks. Malicious users might send
large quantities of forged voice packets to consume the voice VLAN bandwidth, affecting normal
voice communication.
• Security mode: Only voice packets whose source MAC addresses match the recognizable OUI
addresses can pass through the voice VLAN-enabled inbound port, while all other packets are
dropped.
In a safe network, you can configure the voice VLANs to operate in normal mode, reducing the
consumption of system resources due to source MAC addresses checking.
TIP:
HP does not recommend that you transmit both voice traffic and non-voice traffic in a voice VLAN. If you
must transmit both voice traffic and nonvoice traffic, ensure that the voice VLAN security mode is disabled.
Table 17 How a voice VLAN-enabled port processes packets in security and normal mode
Voice VLAN
mode
Packet type Packet processing mode
Untagged packets
Packets that carry the
voice VLAN tag
If the source MAC address of a packet matches an OUI
address configured for the device, it is forwarded in the voice
VLAN. Otherwise, it is dropped.
Security mode
Packets that carry other
tags
Forwarded or dropped depending on whether the port allows
packets of these VLANs to pass through.
Untagged packets
Packets that carry the
voice VLAN tag
The port does not determine the source MAC addresses of
inbound packets. In this way, both voice traffic and non-voice
traffic can be transmitted in the voice VLAN.
Normal mode
Packets that carry other
tags
Forwarded or dropped depending on whether the port allows
packets of these VLANs to pass through.
Configuring a voice VLAN
Configuration prerequisites
Before you configure a voice VLAN, complete the following tasks:
• Create a VLAN
• Configure QoS priority settings for voice VLAN traffic on an interface before enabling voice VLAN
on the interface.
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