A Layer 3 switch, also known as a routing switch, is a coupling element that processes and forwards data packets on the network layer and the link layer. This primarily involves the transmission of IP datagrams over switched networks.
As a router switch, a layer 3 switch is a combination of router and switch. In contrast to a router, a layer 3 switch does not forward data packets via software, but via fast switching units. In addition, Layer 3 switches evaluate the complete network address, whereas routers use only the network part of the address for pure transit. These switches build routing tables and can bundle several ports into a logical subnet. Port switching is then performed at the data link layer. Layer 3 switches are primarily used for micro- segmentation of local area networks( LAN) for the purpose of network tuning. By reducing the size of the LAN segments, higher data throughput is achieved during microsegmentation.
The advantage of Layer 3 switches over router solutions lies in the lower latency and higher data throughput, which is due to the time-consuming store-and-forward process common to routers. With IP switching, data rates of `20^6` packets/s are achieved; values that are many times higher than with routing. In addition, the advantages lie in error and broadcast separation as well as in the use of Layer 3 structure and redundancy procedures such as Hot Standby Router Protocol( HSRP) and Virtual Router Redundancy Protocol( VRRP).
A Layer 3 switch is of particular interest in the formation of VLANs and, in conjunction with Dynamic Host Configuration Protocol( DHCP) and provides the basis for switching delay-sensitive and sensitive traffic flows in Ethernet.