Weidmuller Wireless Ethernet Modem & Device Server WI-MOD-E-G/A User Manual
Rev.
2.16
www.weidmuller.com
64
3.23 - VLAN
What is VLAN
VLAN (Virtual Local Area Network) is a way of splitting a network into groups that could extend beyond a single traditional
LAN to groups of LANs each identified with a different VLAN ID (VID). Using a VLAN, you can group users by logical
connections instead of physical location; this can increase security and help improve the efficiency of traffic flow by
limiting multicast and broadcast messages. Traffic between VLANs is blocked unless the VLAN is identified with the
correct VLAN ID.
There are three main VLAN modes that the WI-MOD-E supports
VLAN (Pass-through Mode)
– A transparent bridge in which frames are forwarded unmodified. This is the default
mode of the modem in which all frames pass transparently through the bridge regardless of whether they are
VLAN tagged or untagged. This is the most common VLAN mode and requires no VLAN configuration at all. In
VLAN Pass-through Mode, access to the internal management functions is via untagged frames only, using the IP
Address and Subnet Mask configured on the Network page.
VLAN Aware (Bridging Mode)
– A VLAN Bridge that allows only explicitly configured VLAN’s that correspond to
the configured VLAN groups to pass data. VLAN Bridging mode is used when the tagging method is changed in a
bridged network, i.e. if a frame traverses from a VLAN group to an interface that is not configured in a VLAN.
When a VLAN packet is passed to an untagged VLAN interface, the tag is removed so that the packet can
properly enter the network. Likewise if an untagged VLAN packet is passed to a VLAN group a VLAN Tag is
added. When one or more VLAN Groups have been configured, VLAN Pass-through is disabled and VLAN Aware
Mode is enabled.
VLAN Aware (Routing Mode)
– Same as “VLAN Aware (Bridging Mode)” above, however VLAN’s are routed not
bridged. When a packet is routed from one VLAN to another on a different interface. The interfaces can be tagged
or untagged and are generally on different subnets.
Enabling VLAN’s will allow the module to facilitate a number of possible VLAN topologies such as:
Segregating a wireless network into multiple virtual networks
Function as the wireless backbone on a VLAN trunk
Enable a wireless network or part of the wireless network to form a VLAN trunk
Define multiple virtual networks, each with a different priority to define traffic class based forwarding behaviour
over the radio channel.
Each module can be setup to accept different networks by configuring VLAN Groups and having the interfaces (Ethernet,
Wireless, WDS Repeater, etc.) configured to accept or reject Tagged or Untagged communications frames.
Operation
VLAN Pass-through is enabled by default in the modem. No VLAN
configuration is needed and modem will happily pass any VLAN tagged
frames.
To initiate VLAN Bridge or Router operation, VLAN Aware mode must
be enabled on the VLAN page.
When “VLAN Aware” is enabled a default “Management VLAN Group”
is created bridging the Ethernet and Wireless interfaces and configuring
both with untagged frames. The “Management IP” and “Management
Netmask” addresses will override the modules “IP Address” and
“Subnet Mask” and the Device Mode will be changed to “VLAN Bridge”;
these changed will be indicated on the Network page of the module. A
Management VLAN is created to ensure that the module will be
accessible for configuration and diagnostics after setup.
Figure 56 - VLAN Pass-through
