Moxa Technologies Moxa EtherDevice Switch EDS-508 - Manual (Page 52)

EDS-508 Series User’s Manual Featured Functions
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specify that the new port is on VLAN Marketing. You do not need to carry out any
re-cabling.
# VLANs provide extra security: Devices within each VLAN can only communicate with
other devices on the same VLAN. If a device on VLAN Marketing needs to communicate
with devices on VLAN Finance, the traffic must pass through a routing device or Layer 3
Switch.
# VLANs help to control traffic: With traditional networks, congestion can be caused by
broadcast traffic that is directed to all network devices whether they require it or not.
VLANs increase the efficiency of your network because each VLAN can be set up to
contain only those devices that need to communicate with each other.
VLANs and MOXA EtherDevice Switch
Your EDS provides support for VLANs using the IEEE Std 802.1Q-1998. This standard allows
traffic from multiple VLANs to be carried across one physical link. The IEEE Std 802.1Q-1998
allows each port on your EDS to be placed in:
# Any one VLAN defined on the EDS.
# Several VLANs at the same time using 802.1Q tagging.
The standard requires that you define the 802.1Q VLAN ID about each VLAN on your EDS before
the Switch can use it to forward traffic:
The Management VLAN
A new or initialized EDS contains a single VLAN—the Default VLAN. This VLAN has the
following definition:
# VLAN Name—Management VLAN
# 802.1Q VLAN ID—1 (if tagging is required)
All the ports are initially placed in this VLAN, and it is the only VLAN that allows you to access
the management software of the EDS over the network.
Communication Between VLANs
If the devices connected to a VLAN need to communicate to devices on a different VLAN, a
router or Layer 3 switching device with connections to both VLANs needs to be installed.
Communication between VLANs can only take place if they are all connected to a routing or
Layer 3 switching device.
VLANs: Tagged and Untagged Membership
Your EDS supports 802.1Q VLAN tagging, a system that allows traffic for multiple VLANs to be
carried on a single physical (backbone, trunk) link. When setting up VLANs you need to
understand when to use untagged and tagged membership of VLANs. Quite simply, if a port is on
a single VLAN it can be an untagged member, but if the port needs to be a member of multiple
VLANs, tagged membership must be defined.
Typically end-stations (for example, clients) will be untagged members of one VLAN, defined as
“Access Port” in EDS, while inter-Switch connections will be tagged members of all VLANs,
defined as “Trunk Port” in EDS.
The IEEE Std 802.1Q-1998 defines how VLANs operate within an open packet-switched network.
An 802.1Q compliant packet carries additional information that allows a switch to determine
which VLAN the port belongs to. If a frame is carrying the additional information, it is known as a
tagged frame.
To carry multiple VLANs across a single physical (backbone, trunk) link, each packet must be