Allied Telesis AT-S101 - Manual (Page 48)

Chapter 3: Virtual LANs
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Each port of a port-based VLAN can belong to as many VLANs as
needed. Therefore, traffic can be forwarded to the members of the groups
which the port is assigned to. For example, port 1 and port 2 are members
of group 1 and ports 1 and 3 are members of group 2. In this case, traffic
from port 1 is forwarded to ports 2 and 3, traffic from port 2 is forwarded
only to port 1, and traffic from port 3 is forwarded only to port 1.
General Rules for Creating a Port-based VLAN
Below is a summary of the general rules to observe when creating a port-
based VLAN.
ˆ Assign a name to each port-based VLAN.
ˆ Assign each port-based VLAN a Group ID.
ˆ The AT-GS950/8POE switch can support up to 52 port-based VLANs.
Tagged VLAN
Overview
The second type of VLAN supported by the AT-S101 Management
Software is the tagged VLAN. In this type of VLAN, membership is
determined by information within the frames that are received on a port
and the VLAN configuration of each port.
The VLAN information within an Ethernet frame is referred to as a tag or
tagged header. A tag, which follows the source and destination addresses
in a frame, contains the Group ID of the VLAN to which the frame belongs
(IEEE 802.3ac standard). This number uniquely identifies each VLAN in a
network.
When a switch receives a frame with a VLAN tag, referred to as a tagged
frame, the switch forwards the frame only to those ports whose Group ID
equals the VLAN tag.
A port that receives or transmits tagged frames is referred to as a tagged
port. Any network device connected to a tagged port must be IEEE
802.1Q-compliant. This is the standard that outlines the requirements and
standards for tagging. The device must be able to process the tagged
information on received frames and add tagged information to transmitted
frames.
A tagged VLAN consists of the following:
ˆ VLAN Name
ˆ Group ID
ˆ Tagged and Untagged Ports
ˆ Port VLAN identifier (PVID)