The Benefits of Virtual LANs
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The Benefits of Virtual LANs
R
emember that layer 2 switches break up collision domains and that
only routers can break up broadcast domains. However, virtual LANs can
be used to break up broadcast domains in layer 2 switched networks. Rout-
ers are still needed in a layer 2 virtual LAN switched internetwork to allow
the different VLANs to communicate with each other.
There are many benefits to creating VLANs in your internetwork.
Remember that in a layer 2 switched network, the network is a flat network,
as shown in Figure 3.1. Every broadcast packet transmitted is seen by every
device on the network, regardless of whether the device needs to receive the
data or not.
F I G U R E 3 . 1
A flat network structure
In a flat network, your only security consists of passwords, and all users
can see all devices. You cannot stop devices from broadcasting or users from
trying to respond to broadcasts. Your security consists of passwords on the
servers and other devices.
By creating VLANs, you can solve many of the problems associated with
layer 2 switching.
Broadcast Control
Broadcasts occur in every protocol, but how often they occur depends upon
the protocol, the application(s) running on the internetwork, and how these
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· Each segment has its own collision domain.
· All segments are in the same broadcast domain.
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