EDS-728 Series User’s Manual
Featured Functions
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VLANs and Moxa EtherDevice Switch
Your EDS-728 provides support for VLANs using 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
standard allows each port on your EDS-728 to be placed in:
y
Any one VLAN defined on the EDS-728.
y
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-728
before the switch can use it to forward traffic:
Managing a VLAN
A new or initialized EDS-728 contains a single VLAN—the Default VLAN. This VLAN has the
following definition:
y
VLAN Name
—Management VLAN
y
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-728 over the network.
Communication Between VLANs
If 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-728 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. Simply put, 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.
A typical host (e.g., clients) will be untagged members of one VLAN, defined as “Access Port” in
the EDS-728, while inter-switch connections will be tagged members of all VLANs, defined as
“Trunk Port” in the EDS-728.
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
tagged with a VLAN identifier so that the switches can identify which packets belong in which
VLAN. To communicate between VLANs, a router must be used.
The EDS-728 supports two types of VLAN port settings:
y
Access Port:
The port connects to a single device that is not tagged. The user must define the
default port PVID that assigns which VLAN the device belongs to. Once the ingress packet of
this Access Port egresses to another Trunk Port (the port needs all packets to carry tag
information), the EDS-728 will insert this PVID into this packet to help the next 802.1Q
VLAN switch recognize it.
y
Trunk Port:
The port connects to a LAN that consists of untagged devices/tagged devices
and/or switches and hubs. In general, the traffic of the Trunk Port must have a Tag. Users can
also assign PVID to a Trunk Port. The untagged packet on the Trunk Port will be assigned the
