The animated TECHTip Tutorial is available here.

This is a review of Cisco router switching modes. It is recommended that a review of Cisco’s router product line and a detailed understanding of the various router platforms such as small, medium and high-end routers be completed prior to any examination. Cisco uses various types of switching caches to reduce switching delay. In the case of Fast Switching, the Switch Processor is only needed to build a route table for the first packet and NOT needed afterward.

In other cases, such as Autonomous Switching, the packet is encapsulated and returned to the Interface Process Buffer without being sent to the Route Processor.

In the case of Fast Switching, the Switch Processor is only needed to build a route table for the first packet and NOT needed afterward. If the first packet is error-free it is then sent to the Switch Processor. A check is made against other switching caches - Autonomous or Silicon for an existing entry. If an entry exists, then Fast Switching is used - explanation follows. The packet is compared with the route table and a route or exit Interface Buffer port is assigned. Subsequent following packets are switched (routed) to the same destination. This is called Fast Switching as an entry already exists in the routing table and the Switch/Route Processor is NOT needed. This is the default switching option on most Cisco routers though this feature is disabled for diagnostics. A check is made against other switching caches.

If an entry exists, then Fast Switching is used. If a packet with a new route arrives, then the “process” (hence the term) Process Switching begins again.

About TECHtionary
TECHtionary is the World’s first and largest animated library/magazine on technology - Web Hosting Magazine’s Editor’s Choice for Technical Help. TECHtionary produces white papers, magazine articles, in-depth product reviews, training tools, and custom animations. Call 303-594-3047 or e-mail  cross at gocross.com to let us show you how we can help you with exciting new tutorials on your products and services.

[tags]route switching,cisco router,fast switching,switch processor,interface process buffer[/tags]