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Looking Backwards at Traditional Campus Networks
9
our networks would be nothing without them. We'll get to that later in this
chapter--trust me.
Virtual LANs
With this new 20/80 rule, more and more users need to cross broadcast
domains (VLANs), and this puts the burden on routing, or layer 3 switching.
By using VLANs within the new campus model, you can control traffic pat-
terns and control user access easier than in the traditional campus network.
Virtual LANs break up broadcast domains by using either a router or switch
that can perform layer 3 functions. Figure 1.3 shows how VLANs are created
and might look in an internetwork.
F I G U R E 1 . 3
VLANs break up broadcast domains in a switched internetwork.
Chapter 3 includes detailed information about VLANs and how to con-
figure them in an internetwork. It is imperative that you understand VLANs
because the traditional way of building the campus network is being rede-
signed and VLANs are a large factor in building the new campus model.
VLAN1
VLAN3
VLAN2
VLAN4
E0
E1
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