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Types of VLANs
802.1Q VLAN User’s Guide 1-3
1.2 TYPES OF VLANs
There are a number of different strategies for creating Virtual Local Area
Networks, each with their own approaches to defining a station’s
membership in a particular VLAN.
1.2.1 802.1Q VLANs
An 802.1Q VLAN switch determines the VLAN membership of a data
frame by its Tag Header, described later in this chapter. If the frame
received is not tagged, the switch classifies the frame into the VLAN that
is assigned as the default VLAN of the switch.
Some or all ports on the switch may be configured to operate as GARP
VLAN Registration Protocol (GVRP) ports. If a frame received is tagged,
the frame is forwarded to the GVRP ports that are configured to transmit
frames associated with the frame VLAN ID and protocol. If the received
frame is not tagged, the frame is examined and tagged as belonging to the
default VLAN. Then the frame is forwarded to the GVRP ports that are
configured to transmit frames associated with the default VLAN and the
frame protocol.
1.2.2 SecureFast VLANs
Cabletron Systems’ SecureFast VLAN strategy takes a different approach
to creating virtual LANs. In a SecureFast VLAN environment, the
switches in the network recognize Network Layer routing requests and
translate them. Based on this translation, the switches set up a connection
between the end devices in the network.
1.2.3 Other VLAN Strategies
VLANs may also be created by a variety of addressing schemes,
including the recognition of groups of MAC addresses or types of traffic.
One of the best-known VLAN-like schemes is the use of IP Subnets to
divide networks into smaller subnetworks.