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92 Chapter 3: Switched/Campus LAN Solutions
The Role of LAN Switching Technology in Campus Networks
The CCDP can integrate switching devices into his or her existing shared-media networks to
achieve the following goals:
·
Reduce congestion and increase the available bandwidth for each user
·
Organize users into logical workgroups
·
Deploy multimedia applications across different switching platforms and technologies
·
Reduce the costs of managing network operations
·
Provide scalability, traffic control, and security
Layer 3 Switching
Layer 3 switches were developed to address the user's changing bandwidth requirements. The
introduction of the Layer 3 switch has created a significant amount of debate with regard to the
definitions of a switch and a router. Layer 3 switches do not adhere to the classic definition of
a switch.
Depending on the vendor, there are Layer 3 switches available that function at Layer 3 of the
OSI model and that have routing functionality equal to or greater than routers currently in use.
These Layer 3 switches are designed to combine the speed of switching with the scalability of
routing.
Layer 3 switches perform three major functions: packet switching, route processing, and
provisioning of intelligent network services. Although they are specifically tailored for a
campus LAN environment, Layer 3 switches actually perform most functions that routers have
traditionally performed.
For CCDP test purposes, the term switch refers to hardware-based platforms that function at
Layer 2.
Bridges and Switches
Although bridges and switches share many features at the data-link layer, there are significant
differences between them. Because bridges switch in hardware, they are much faster than their
software-switching counterparts. Switches can interconnect LANs of different bandwidths and
can support higher fast-density ports than bridges. Switches can also support VLANs.
Switching technology has replaced bridging technology as the Layer 2 internetworking solution
of choice. Switching implementations now dominate applications in which bridging
technologies were implemented in prior network designs. Superior throughput performance,
higher port density, lower per-port cost, and greater flexibility have contributed to the
emergence of switches as replacement technology for bridges and as complements to
routing technology.
87200333.book Page 92 Wednesday, August 22, 2001 2:18 PM