User`s guide

Types of VLANs
DIGITAL MultiSwitch 700 Port Based 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 Port Based VLANs
A port based VLAN switch determines the membership of a data frame
by examining the configuration of the port that received the transmission
or reading a portion of the data frame’s tag header. A four-byte field in the
header is used to identify the VLAN. This VLAN identification indicates
what VLAN the frame belongs to. If the frame has no tag header, the
switch checks the VLAN setting of the port that received the frame. If the
switch has been configured for port based VLAN support, it assigns the
port’s VLAN identification to the new frame.
1.2.2 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. These other VLAN types offer
performance advantages and disadvantages that can be quite different
from those available with the port based VLAN strategy.
1.3 BENEFITS AND RESTRICTIONS
The primary benefit of the port based VLAN technology is the
localization of traffic that it provides. This function can offer
improvements in security and performance to stations assigned to a
VLAN.
While the localization of traffic to VLANs can improve security and
performance, it imposes some restrictions on network devices that
participate in the VLAN. If a switch is operating in the “secure mode,” a