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TRENDnet User’s Guide

TEG-S50ES

Voice VLAN

Configuring Voice VLANs

Network > Voice VLAN

This chapter contains a description of the Switch’s Voice VLAN feature and the
procedures to create, modify, and delete a voice VLAN configuration.

The Voice VLAN feature is specifically designed to maintain high quality, uninterrupted
voice traffic through the switch. When talking on a voice over IP phone, a user expects
to have no interruptions in the conversation and excellent voice quality. The Voice VLAN
feature can be configured to meet these requirements.

CoS with Voice VLAN

The Voice VLAN CoS parameter maintains the voice quality between the ingress and
egress ports of the switch. CoS must be enabled for the Voice VLAN CoS priority to take
effect. The CoS priority level that you config is applied to voice traffic on all ports of the
voice VLAN. Normally, most (non-Voice) Ethernet traffic transverses the switch through
lower order egress queues. To avoid delays and interruptions in the voice data flow, the
CoS priority level assigned to the voice VLAN should be mapped to a higher order queue
and the scheduling algorithm should be set to Strict Priority. These settings ensure that
the voice data packets are processed before other types of data so that the voice quality
is maintained as the voice data passes through the switch.

Organization Unique Identifier (OUI)

Each IP phone manufacturer can be identified by one or more Organization Unique
Identifiers (OUIs). An OUI is three bytes long and is usually expressed in hexadecimal
format. It is imbedded into the first part of each MAC address of an Ethernet network
device. You can find the OUI of an IP phone in the first three complete bytes of its MAC
address.

Typically, you will find that all of the IP phones you are installing have the same OUI in
common. The switch identifies a voice data packet by comparing the OUI information in
the packet’s source MAC address with an OUI table that you configure when you initially
set up the voice VLAN. This is important when the Auto-Detection feature for a port and
is a dynamic voice VLAN port.

When you are configuring the voice VLAN parameters, you must enter the complete
MAC address of at least one of your IP phones. An “OUI Mask” is automatically
generated and applied by the Web Management Utility software to yield the

manufacturer’s OUI. If the OUI of the remaining phones from that manufacturer is the
same, then no other IP phone MAC addresses need to be entered into the configuration.

However, it is possible that you can find more than one OUI from the same
manufacturer among the IP phones you are installing. It is also possible that your IP
phones are from two or more different manufacturers in which case you will find
different OUIs for each manufacturer. If you identify more than one OUI among the IP
phones being installed, then one MAC address representing each individual OUI must be
configured in the voice VLAN. You can enter a total of 13 OUIs.

Dynamic Auto-Detection vs Static Ports

Note: This switch only supports Auto-Detection for simplicity purposes.

Prior to configuring the voice VLAN, you must configure a tagged VLAN which is the
basis for the voice VLAN configuration. The VLAN must be configured with one or more
tagged or untagged ports that will serve as the voice VLAN uplink/downlink. By default,
a tagged or untagged port is a static member of a tagged VLAN. The ports that you
choose to configure as dynamic Auto-Detection ports must be connected directly to an
IP phone. When you initially define the ports of a tagged VLAN for your voice VLAN
configuration, they must be configured as a “Not Member” ports. The “Not Member”
ports are eligible to dynamically join the voice VLAN when voice data is detected with a
predefined OUI in the source MAC address. The port will leave the voice VLAN after a
specified timeout period. This port behavior is configured with the voice VLAN Auto-
Detection feature.

For the Auto-Detection feature to function, your IP phone(s) must be capable of
generating 802.1Q packets with imbedded VLAN ID tags. You must manually configure
your IP phone(s) for the same VLAN ID as the switch’s voice VLAN ID. When voice data is
detected on one of the “Not Member” ports, the packets from the IP phone will contain
the voice VLAN ID so they are switched within the switch’s voice VLAN.

One or more ports in your voice VLAN must be configured as Static tagged or untagged
members. Static VLAN members are permanent member ports of the voice VLAN and
there is no dependency on the configuration of the devices connected to the ports.
These ports might be connected to other voice VLAN network nodes such as other
Ethernet switches, a telephone switch, or a DHCP server. The voice VLAN Auto-
Detection feature cannot be enabled on Static tagged or tagged ports.

Note: Any Static tagged members of the voice VLAN are required to have the port VLAN
ID (PVID) configured to be the same as the voice VLAN ID. This insures that all untagged
packets entering the port are switched within the voice VLAN as the voice data passes
through the switch.