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Chapter 6
Virtual LANs (VLANs)
F I G U R E 6 . 7
Router with individual VLAN associations
Instead of using a router interface for each VLAN, you use one Fast Ethernet
interface and run ISL routing. Figure 6.8 shows how a Fast Ethernet interface
on a router will look when configured with ISL routing. This allows all VLANs
to communicate through one interface. Cisco calls this "a router-on-a-stick."
F I G U R E 6 . 8
Router-on-a-stick
Summary
T
his chapter introduced you to the world of virtual LANs and
described how Cisco switches can use them. We talked about how VLANs
break up broadcast domains in a switched internetwork, which is important
Router connecting three VLANs
together for inter-VLAN communication,
one interface for each VLAN.
Router connecting all VLANs together
allowing for inter-VLAN communication,
using only one router interface
(Router on a stick).
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