PT-7828 User’s Manual
Featured Functions
3-48
network, and retains its original subnet membership, you only need to specify that the new
port is on VLAN
Marketin
g. You do not need to carry out any re-cabling.
y
VLANs provide extra security.
Devices within each VLAN can only communicate with
other devices on the same VLAN. If a device on VLAN
Marketing
nePT to communicate with
devices on VLAN
Financ
e, the traffic must pass through a routing device or Layer 3 switch.
y
VLANs 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 the PowerTrans
Your PT-7828 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 PT-7828 to be placed as follows:
y
In a single VLAN defined on the PT-7828
y
In several VLANs simultaneously using 802.1Q tagging
The standard requires that you define the
802.1Q VLAN ID
about each VLAN on your PT-7828
before the switch can use it to forward traffic:
Managing a VLAN
A new or initialized PT-7828 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 PT-7828 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 PT-7828 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
PT-7828, while inter-switch connections will be tagged members of all VLANs, defined as Trunk
Port in PT-7828.
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
