Layer 3 Switch

Problems with Routers and Layer 3 Switches:

The problem with using routers to overcome some of the inadequacies of bridge or layer 2 switch is that routers are designed to be implemented at the gateway and only process packets to/from outer networks, and it also typically do all of the IP level processing involved in the forwarding of IP traffic in software.High-speed LANs and high-performance layer 2 switches pump millions of packets per second, where as software based router may only be able to handle well under a millions packet per second.

To accommodate such a load, number of vendors have developed layer 3 switch. It implements the packet forwarding logic of the router in hardware.

There are two categories of layer 3 switch,

1.        Packet by packet It Operates in same way as traditional router, but much faster.
2.      Flow-based: Flow based layer 3 switch tries to enhance performance by identifying flows of IP packets that have same source and destination (Done by observing ongoing traffic or using a special flow label in packet header, IPv6).