Administration
A31003-C1000-M102-5-76A9, 09/2017
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OpenScape Desk Phone CP200/CP205/CP400/CP600 HFA, Administration Manual
administration.fm
LAN Settings
3.2.2
VLAN
VLAN (Virtual Local Area Network) is a technology that allows network administrators to parti-
tion one physical network into a set of virtual networks (or broadcast domains).
Partitioning a physical network into separate VLANs allows a network administrator to build a
more robust network infrastructure. A good example is a separation of the data and voice net-
works into data and voice VLANs. This isolates the two networks and helps shield the endpoints
within the voice network from disturbances in the data network and vice versa.
In a layer 1 VLAN, the ports of a VLAN-aware switch are assigned to a VLAN statically. The
switch only forwards traffic to a particular port if that port is a member of the VLAN that the traffic
is allocated to. Any device connected to a VLAN-assigned port is automatically a member of
this VLAN, without being a VLAN aware device itself. If two or more network clients are con-
nected to one port, they cannot be assigned to different VLANs. When a network client is mov-
ing from one switch to another, the switches’ ports have to be updated accordingly by hand.
With a layer 2 VLAN, the assignment of VLANs to network clients is realized by the MAC ad-
dresses of the network devices. In some environments, the mapping of VLANs and MAC ad-
dresses can be stored and managed by a central database. Alternatively, the VLAN ID, which
defines the VLAN whereof the device is a member, can be assigned directly to the device, e. g.
by DHCP. The task of determining the VLAN for which an Ethernet packet is destined is carried
out by VLAN tags within each Ethernet frame. As the MAC addresses are (more or less) wired
to the devices, mobility does not require any administrator action, as opposed to layer 1 VLAN.
The phone must be configured as a VLAN aware endpoint if the phone itself is a member of the
voice VLAN, and the PC connected to the phone’s PC port is a member of the data VLAN.
There are 3 ways for configuring the VLAN ID:
•
By LLDP-MED
•
By DHCP
•
Manually
3.2.2.1
Automatic VLAN discovery using LLDP-MED
This is the default setting. The VLAN ID is configured by the network switch using LLDP-MED
(Link Layer Discovery Protocol-Media Endpoint Discovery). If the switch provides an appropri-
ate TLV (Type-Length-Value) element containing the VLAN ID, this VLAN ID will be used. If no
appropriate TLV is received, DHCP will be used for VLAN discovery.
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The implementation of a voice network based on VLANs requires the network infra-
structure (the switch fabric) to support VLANs.
