Specifications

VoIP and VLANs
335
Standalone CXi without expansion switch, dedicated voice and data ports
In this configuration, the CXi controller becomes the network, albeit limited to 16 ports. There
are no egress queuing issues since each device, either voice or data, has its own dedicated
port. In this situation, the internal switching bandwidth of the internal Layer 2 switch exceeds
that from the external ports. There is no need for priority mechanisms, hence no requirement
for VLANs.
With this reduced configuration, there is no requirement for VLAN settings.
Expanded CXi, dedicated voice and data ports
This is similar in configuration to the standalone CXi with dedicated voice and data ports. The
biggest difference is the connection between the CXi controller and the expansion Layer 2
switch. This link will be shared between voice and data devices. In practice, if the data
requirements are low, then there should be sufficient bandwidth to run without priority queuing.
However, data demands can vary, and there is a potential for congestion. In this case the voice
traffic should be tagged with the higher priority.
The link between the CXi and expansion Layer 2 switch should have VLAN enabled.
The individual end devices can have VLAN and priority assigned at the ingress point of the
network switches, and may use a common VLAN (and subnet). The priority will obviously be
different. However, this is a physical implementation and requires ports to be reconfigured every
time a device is moved. A general setting can be applied, with the data devices going to the
default VLAN and the voice devices being assigned to the voice VLAN, such as through DHCP,
or manual settings.
In this case the individual access ports should have VLAN enabled.
Common network connection for both voice and data devices
Where voice and data devices share a common connection to the network, there is a mix of
data possible on the connection. On ingress to the network port, the phone will prioritize data.
However, on egress, at the far end connection, this will not occur. Priority marking is needed
to allow the egress priority to be carried through the network.
For this configuration VLAN should be enabled at access and network device
interconnections.
Connection to corporate network
In this case the end devices are likely physically connected to network devices that are remote
from the controller, e.g. different floors, separate building, etc. The connections through the
network will carry a wide range of information, both data and voice. The controller is likely to
be connected to the network at a point normally associated with other server devices. In this
case it will be a voice server, be it a group controller, a voice gateway, or combination thereof.
Connections for the end devices, such as the phones, require VLAN to be enabled, at the
access points.