MCSE : Security Specialist
Describe the main characteristics of VLANs.
A
Virtual LAN is a group of devices on one or more LANs that are
configured using management software so that they can communicate as
if they were attached to the same LAN segment, when in fact they are
located on a number of different segments. Because VLANs are based
on logical instead of physical connections, they are more flexible.
For a
computer to communicate with devices on different LAN segments other
than the segment it is located on, requires the use of a router. And
as networks expand, more routers are needed to separate users into
broadcast and collision domains, and provide connectivity to other
LANs. Since routers add latency, this can result in the delay of
data transfer over the network.
Switches are used in VLANs to create the same division of the
network into separate broadcast domains, but without the latency
problems of a router.
Advantages to using VLANs:
Switched networks increase performance, by reducing the size of
collision domains. Users can be grouped into logical networks which
will increase performance by limiting broadcast traffic to users
performing similar functions or within individual workgroups. Less
traffic needs to be routed, causing the latency added by routers to
be reduced.
VLANs
provide an easier way to modify logical groups in changing
environments. VLANs make large networks more manageable by allowing
centralized configuration of devices located in physically different
locations.
Software configurations can be made across machines with the
consolidation of a department’s resources into a single subnet. IP
addresses, subnet masks, and local network protocols will be more
consistent across the entire VLAN.
VLANs
provide independence from the physical topology of the network by
allowing physically diverse workgroups to be logically connected
within a single broadcast domain.
A
switched network delivers frames only to the intended recipients,
and broadcast frames only to other members of the VLAN. This allows
the network administrator to segment users requiring access to
sensitive information into separate VLANs from the rest of the
general user community regardless of physical location, thus
enhancing security.
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