TN-5516/5518 User’s Manual Featured Functions
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VLANs and the ToughNet switch
Your TN-5500 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 TN-5500 to be placed as follows:
y In a single VLAN defined on the TN-5500.
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 TN-5500
before the switch can use it to forward traffic:
Managing a VLAN
A new or initialized TN-5500 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 TN-5500 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 TN-5500 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
TN-5500, while inter-switch connections will be tagged members of all VLANs, defined as Trunk
Port in TN-5500.
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.
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