User's Manual

C HAPTER 4 | Configuring the Switch
Managing VoIP Traffic
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MANAGING VOIP TRAFFIC
When IP telephony is deployed in an enterprise network, it is
recommended to isolate the Voice over IP (VoIP) network traffic from other
data traffic. Traffic isolation can provide higher voice quality by preventing
excessive packet delays, packet loss, and jitter. This is best achieved by
assigning all VoIP traffic to a single Voice VLAN.
The use of a Voice VLAN has several advantages. It provides security by
isolating the VoIP traffic from other data traffic. End-to-end QoS policies
and high priority can be applied to VoIP VLAN traffic across the network,
guaranteeing the bandwidth it needs. VLAN isolation also protects against
disruptive broadcast and multicast traffic that can seriously affect voice
quality.
The switch allows you to specify a Voice VLAN for the network and set a
service priority for the VoIP traffic. VoIP traffic can be detected on switch
ports by using the source MAC address of packets, or by using LLDP (IEEE
802.1ab) to discover connected VoIP devices. When VoIP traffic is detected
on a configured port, the switch automatically assigns the port as a tagged
member the Voice VLAN. Alternatively, switch ports can be manually
configured.
CONFIGURING VOIP
TRAFFIC
Use the Voice VLAN Configuration page to configure the switch for VoIP
traffic. First enable automatic detection of VoIP devices attached to the
switch ports, then set the Voice VLAN ID for the network. The Voice VLAN
aging time can also be set to remove a port from the Voice VLAN when
VoIP traffic is no longer received on the port.
PATH
Advanced Configuration, Voice VLAN, Configuration
PARAMETERS
These parameters are displayed:
Global Configuration
◆ Mode
3
– Enables or disables Voice VLAN operation on the switch.
(Default: Disabled)
◆ VLAN ID – Sets the Voice VLAN ID for the network. Only one Voice
VLAN is supported on the switch. (Range: 1-4095; Default: 1000)
The Voice VLAN cannot be the same as that defined for any other
function on the switch, such as the management VLAN (see "Setting an
IPv4 Address" on page 46), the MVR VLAN (see "Multicast VLAN
Registration" on page 140), or the native VLAN assigned to any port
(see "Configuring VLAN Attributes for Port Members" on page 175).
3. MSTP must be disabled before the Voice VLAN is enabled (see "Configuring Global
Settings for STA" on page 129), or the Voice VLAN port mode is set to Auto or Forced.
This prevents the spanning tree’s ingress filter from dropping VoIP traffic tagged for the
Voice VLAN.