CCNP: Building Cisco Multilayer Switched Networks Study Guide (642-811)

The architecture of modern switches does not conform to a single model. Vendors, in competition with each other, devise their own mechanisms to create faster, more scalable switches to suit every niche in the modern network. Cisco is no exception; in fact, they are probably among the world's greatest innovators.

New technologies such as the Content Addressable Memory lookup system are used in the entry- level 2950 series switches, and CAM's big brother, the Ternary CAM, is used in the 3550, 4000, and 6500 series. This provides the speedy lookup required for fast decision-making. In turn, this decision- making is itself speeded up by the use of processors external to the memory tables. In the 3550, these are satellite ASICs, and in the 6500 they are provided by the Distributed Forwarding Card.

All of this is bound together by the selection of the most appropriate switching fabric. Whether it is the shared memory of the 2950 and the 4000, the distributed shared memory of the 3550, or the crossbar of the 6500, each switch has a fabric that matches its needs and position in the network. In addition, a range of software options is currently available, with the biggest decisions centering around whether to purchase SI or EI for the 2950, and whether to use hybrid IOS or native IOS on the 4000 and 6500.

Finally, switch management has never been more difficult. With the range of newer technologies such as voice and video demanding newer QoS options, we find ourselves with an almost bewildering array of configuration options. To manage this environment, we have the legacy range of show and debug commands, although debug will be new to many of you without a router background. But we also have the Cisco Cluster Management Suite, which allows us to manage up to 16 switches using a single front end.