EDS-518A Series User’s Manual

Featured Functions

yVLANs 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.

yVLANs help control traffic: With traditional networks, congestion can be caused by broadcast traffic that is directed to all network devices, regardless of whether or not they need it. 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-518A 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-518A to be placed in:

yAny one VLAN defined on the EDS-518A.

ySeveral VLANs at the same time using 802.1Q tagging.

The standard requires that you define the 802.1Q VLAN ID for each VLAN on your EDS-518A before the switch can use it to forward traffic:

Managing a VLAN

A new or initialized EDS-518A contains a single VLAN—the Default VLAN. This VLAN has the following definition:

yVLAN Name—Management VLAN

y802.1Q VLAN ID—1 (if tagging is required)

All the ports are initially placed on this VLAN, and it is the only VLAN that allows you to access the management software of the EDS-518A 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

EDS-518A 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 EDS-518A, while inter-switch connections will be tagged members of all VLANs, defined as “Trunk Port” in EDS-518A.

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. 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 to which VLAN. To communicate between VLANs, a router must be used.

MOXA EDS-518A supports two types of VLAN port settings:

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