Multilayer Switching (MLS)

Multilayer Switching (MLS)
Multilayer switching (MLS) combines layer 2, 3, and 4 switching technologies and provides
high-speed scalability with low latency. It accomplishes this combination of high-speed
scalability with low latency by using huge filter tables based on the criteria designed by the
network administrator.
Multilayer switching can move traffic at wire speed and also provide layer 3 routing, which
can remove the bottleneck from the network routers. This technology is based on the concept
of route once, switch many.
394 Chapter 12  The Campus Network
Multilayer switching can make routing/switching decisions based on the following:
 MAC source/destination address in a Data Link frame
 IP source/destination address in the Network layer header
 Protocol field in the Network layer header
 Port source/destination numbers in the Transport layer header
There is no performance difference between a layer 3 and a layer 4 switch because the routing/
switching is all hardware based.
MLS will be discussed in more detail in Chapter 18, “Multilayer Switching.”
It is important that you have an understanding of the different OSI layers and what they provide
before continuing on to the Cisco three-layer hierarchical model.