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LAN & WAN Basics

Introduction

It wasn't too long ago that the basic premise of this article—using a managed switch in a home / SOHO network—would have had a pretty limited audience. After all, if you only spent $50 or so for a router, why pay hundreds of dollars for a switch?

But prices have come down dramatically, as feature sets and ease of use have expanded and improved. With eight-port Gigabit "smart" switches now available for under $100, the question may be more "Why not?" than "Why?".

In this series, I'll first provide a brief tutorial on what makes a smart switch "smart". But most of the focus will be on going through the feature set of a typical inexpensive switch and providing examples of why you might want to use particular features and how to do it.

But first, let's define "smart" and "managed" switches. Basically, smart / managed switches have features that can be configured to perform network management functions. These functions can be as simple as setting the link speed of a port or disabling it entirely, or more complex like limiting bandwidth or grouping devices into VLANs.

At this point, the difference between "smart" and a "managed" switches is strictly marketing. The term "smart" switch was coined when network product manufacturers first introduced lower-priced managed switches. Part of the reason for the new term was to just get some attention for these new products. But a more important reason was to attempt to create a differentiation between the new (and typically less-expensive) devices and older (and typically more expensive) products.

When smart switches first appeared, they typically had fewer features than managed switches and were managed via web interfaces instead of the Telnet / command line interfaces. But, as I noted earlier, the feature sets of smart switches have expanded, so that now you have to look pretty closely to see a difference between similarly-priced managed and smart switches. For all intents and purposes, you can now use the terms interchangeably.

One thing you do have to pay attention to, however, is a switch's OSI Layer of operation. In general, smart switches are Layer 2 devices, just like unmanaged switches. Both operate at the Data Link layer, which handles physical addressing. Simply put, Layer 2 devices can look only at the MAC address and LLC portions of a data packet's Ethernet frame.

Ethernet Type II Frame

Figure 1: Ethernet Type II Frame (courtesy Wikipedia)

On the other hand, you can find managed switches in both Layer 2 and Layer 3 flavors. Layer 3 switches operate at the Network Layer, which provides network path determination and logical addressing functions. In most cases, this means that Layer 3 switches handle packets based on their IP address, which allows them to perform basic routing functions. That's all I'm going to say about Layer 3 switches, which are way beyond the requirements (and budget) of small networks.

NETGEAR GS108T

Two popular eight-port smart switches under $100 are Cisco's SLM2008 and NETGEAR's GS108T. I'm going to use the GS108T (Figure 2) for this series since I have one on long-term loan for testing NAS link aggregation.

NETGEAR's GS108T

Figure 2: NETGEAR's GS108T

The GS108T is a managed version of NETGEAR's popular unmanaged GS108. Both have eight auto MDI/X 10/100/1000 ports with front-mounted connectors with integrated link / activity LEDs. I prefer front-mounted ports because I'm constantly connecting and disconnecting devices. But if you like rear-mounted ports, the Cisco SLM2008 has you covered.

Figure 3 is a photo of the GS108T's board. You can see only the Broadcom BCM5836P Communications Processor, 16 MB of RAM and 4 MB of flash. The switch itself under the heatsink is a BCM5398 8-Port GbE Switch with 8 Integrated PHYs and LoopDTech.

GS108T board
Click to enlarge image

Figure 3: GS108T board

NETGEAR has implemented a uniform interface for their web-managed switches. The System Information login landing pages for the GS108T (Figure 4) and an older FS728TS 10/100 smart switch (Figure 5), updated with Version 3 series firmware, illustrate the family resemblance

GS108T System Information

Figure 4: GS108T System Information

 

FS728TS System Information

Figure 5: FS728TS System Information

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