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I
n this chapter, we'll discuss Multi-Layer Switching (MLS), which
is part of the Bridging/Switching group of topics outlined by Cisco for the
Switching exam (640-504).
Why MLS? Why do you need layer 3 switching when you have layer 3
routing? The answer to both of these questions is simple: enhanced perfor-
mance. Why do you implement any features on any piece of Cisco equip-
ment? To increase performance and take advantage of the robust feature set
provided by Cisco.
Fundamentals of MLS
Y
ou have undoubtedly heard of the term "router on a stick." Figure 7.1
depicts the router on a stick architecture. As you can see from the diagram,
there are multiple hosts using two separate VLAN assignments. One segment
is running on VLAN10, and the other segment is running on VLAN50. Both
VLANs, or segments, are connected to the same switch. The switch is then
connected to a router. Here we show an external router, but an RSM pro-
vides the same functionality, just internally.
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