EDS-508A/505A Series User’s Manual
Featured Functions
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Managing a 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 on 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 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
The 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. 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, while inter-switch connections will be tagged members of all VLANs, defined as “Trunk
Port” in the 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. 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.
The EDS 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 determines to which VLAN the device belongs. Once the ingress packet
of this Access Port egresses to another Trunk Port (the port needs all packets to carry tag
information), the EDS 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.