D-Link DGS-3308FG Product Manual - Page 12
Introduction
UPC - 790069239373
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8-port Gigabit Ethernet Switch User's Guide 1 INTRODUCTION This section describes the Layer 3 functionality and Layer 2 and Layer 3 features of the DGS-3308 Series switches. 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. For a more detailed discussion of the functionality of the DGS-3308, please see Chapter 5, "Switch Management and Operating Concepts." 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 DGS-3308 Layer 3 switch has eight Gigabit Ethernet ports, including two which are GBIC-based. Where a traditional router would have one or two high-speed serial WAN connections, the DGS-3308 relies upon Gigabit Ethernet ports to connect to a separate device, which in turn, connects the network to a WAN or the Internet. The DGS-3308 can be thought of as 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 DGS-3308FG can also replace key traditional routers for data centers and server farms, routing between these locations and the rest of the network, and providing eight ports of Layer 2 switching performance combined with wire-speed routing. Backbone routers can also be replaced with DGS-3208FG and DGS-3208TG switches and a series of DGS-3308 switches could be linked via the Gigabit Ethernet ports. Routers that service WAN connections would remain in place, but would now be removed from the backbone and connected to the DGS-3308 via a Gigabit Ethernet port. The backbone itself could be migrated to Gigabit Ethernet, or faster technologies as they become available. Policy services can then be introduced (or enhanced) in the backbone infrastructure and maintained throughout the network - even to the desktop. With a distributed infrastructure and a logical management structure, network performance becomes easier to measure and fine-tune. With the completion of the migration of the backbone to Gigabit or higher-performance technologies, the result is inherently scalable and easily evolved for future technologies. This core network will also become the termination point for Virtual Private Networks (VPNs) for remote office access to the enterprise infrastructure. The DGS-3308 can then be thought of as accomplishing 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 2