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DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
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INTRODUCTION
This section describes the Layer 3 functionality and Layer 2 and Layer 3 features of the DES-3326.
Some background information about Ethernet/Fast Ethernet, Gigabit Ethernet, and switching
technology is presented. This is intended for readers who may not be familiar with the concepts of
layered switching and routing but is not intended to be a complete or in-depth discussion.
Layer 3 Switching
Layer 3 switching is the integration of two proven technologies: switching and routing. In fact, Layer 3
switches are running the same routing routines and protocols as traditional routers. The main
difference between traditional routing and Layer 3 switching is the addition of a group of Layer 2
switching domains and the execution of routing routines for most packets via an ASIC – in hardware
instead of software.
Where a traditional router would have one, or at best a few, Fast Ethernet ports, the DES-3326 Layer 3
switch has 24 Fast Ethernet ports and optionally, 2 Gigabit Ethernet ports. Where a traditional router
would have one or two high-speed serial WAN connections, the DES-3326 relies upon a Fast Ethernet
port to connect to a separate device, which in turn, connects the network to a WAN or the Internet.
The DES-3326 can be thought of as 24 Fast Ethernet Layer 2 switching domains with a wire-speed
router between each domain. It can be deployed in a network between a traditional router and the
intranetwork. The traditional router and its associated WAN interface would then handle routing
between the intranetwork and the WAN (the Internet, for example) while the Layer 3 switch would
handle routing within the LAN (between the Fast Ethernet Layer 2 domains). Any installed Layer 2
switches, and indeed the entire subnetting scheme, would remain in place.
The DES-3326 can also replace key traditional routers for data centers and server farms, routing
between these locations and the rest of the network, and providing 24 ports of Layer 2 switching
performance combined with wire-speed routing.
Backbone routers can also be replaced with DES-3326 and a series of DES-3326 could be linked via
the optional Gigabit Ethernet ports. Routers that service WAN connections would remain in place, but
would now be removed from the backbone and connected to the DES-3326 via an Ethernet/Fast
Ethernet port. The backbone itself could be migrated to Gigabit Ethernet, or faster technologies as they
become available.
The DES-3326 accomplishes two objectives. First as a tool to provide high-performance access to
enterprise data servers and infrastructure, and second, to enhance the performance of network
equipment already installed. Many network segments display poor performance, but the Ethernet wire
is only carrying a fraction of its total traffic capacity. The problem is not the network, but the ability of
the connected devices utilize the full capacity of the network. The DES-3326 can eliminate network
bottlenecks to high-traffic areas, and improve the utilization of the network’s installed bandwidth.
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