1.2 Key Characteristics of Various Switching Technologies
1.2.5 Multilayer switching

MultiLayer Switching (MLS) combines Layer 2 switching and Layer 3 routing functionality. MLS moves campus traffic at wire speed while at the same time satisfying Layer 3 routing requirements. This combination not only solves throughput problems, but also removes the conditions under which Layer 3 bottlenecks form. MLS is based on a "route once, switch many" model, as shown in Figure .

This feature has become a highly desired method of accelerating routing performance through the use of dedicated ASICs. Traditional routing is carried out as a combined effort between software and the CPU; MLS offloads a significant portion of routing to hardware.

MLS can operate at Layer 3 or 4. When operating as a Layer 3 switch, the switch caches flows based on IP addresses. When operating as a Layer 4 switch, the switch caches conversations based on source address, destination address, source port, and destination port.