User`s manual

EDS-828 Series Featured Functions
3-42
VLANs and Moxa EtherDevice Switch
Your EDS-828 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-828 to be placed in:
• Any one VLAN defined on the EDS-828.
• 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-828 before the switch
can use it to forward traffic:
Managing a VLAN
A new or initialized EDS-828 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-828 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-828 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-828,
while inter-switch connections will be tagged members of all VLANs, defined as “Trunk Port” in the EDS-828.
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-828 supports two types of VLAN port settings:
• 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-828 will insert this PVID
into this packet to help the next 802.1Q VLAN switch recognize it.
• 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 port default PVID as its VID.
The following section illustrates how to use these ports to set up different applications.