Know Your Network: Switches, Bridges, and Routers: Page 2

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The Bridge

Given the switch's capabilities, you would think that a bridge would be a redundant piece of hardware given that it performs many of the same functions... and you'd be correct.

The network bridge is designed to seamlessly connect two or more smaller network segments into one harmonious whole. They generally contain fewer physical ports, but with switches able to play the same role, you'll likely find the latter keeping things together on your networks.

Plugging your LAN segments into the same bridge/switch does make getting your networks talking to each other a simple process and the link speed controls can come in handy when you have to share those Internet links with several dozen, or hundreds, of machines.

Another thing you'll want to keep your eye on when dealing with multiple networks being bridged is just how much traffic is passing through them and how many connections it's going to be tracking. The requirements are exponential so you'll be looking at some robust gear such as Cisco's Catalyst 2960 series of switches for small to medium sized needs while enterprise endeavors are no doubt mulling over Cisco Nexus 7000 switches.

The Router

Seeing as the trend is to build upon the smaller segments of a network in order to get to the next big thing, you'll invariably hit the router - the granddaddy of network devices.

A home router, for instance, will typically connect a few computers to the Internet at large, passing on the data you generated to your ISP for forwarding to its destination. Along the way it's bound to hit sophisticated pieces of equipment designed to handle quite a bit more data than your connection can muster.

Cisco XR 12000 RouterRouters operate on Layer 3 of the OSI Model, which handles figuring out the optimal path for your data to reach its endpoint. Switches/bridges function on layer two, which determines the quickest way to deliver the information that it is keeping track of by matching up a connected device's MAC Address with the IP Address it was communicating with.

Routers are far more interested in the IP Address that data packets are destined to be delivered to and the priority of the information being sent, usually set by the router's maintainer.

Those IP Addresses are, of course, doled out in large blocks to Internet Service Providers, institutions and corporations at large so there are a ton of them. So many in fact that the old IPv4 standard is quickly running out of usable numbers, given the number of Internet capable devices and people receiving Internet service the old 32 bit addresses is making way for IPv6 which boasts many more workable addresses.

The focus on simply delivering the data simplifies things a tiny bit for this workhorse, giving it more free time to learn routing information from any other routers connected to it or in close enough proximity, thereby allowing your data to be sent over the best possible path. Should that path not be available due to, say, construction equipment somehow severing important connections, the router will select the next best link.

These machines tend to be located where large clusters of smaller networks reside or even high powered blocks of servers that require a generous amount of bandwidth in order to operate optimally. If you are beyond the point of wiring a small business, you're likely scoping out hardware like the Cisco 2800 series of routers. At the very high-end, are Cisco routers like the XR 12000 series pictured above.

Although synonymous with networking, Cisco isn't the only game in town. Outfits like Juniper Networks, 3Com and Foundry Networks, to name a few, compete hard for your computer networking budget.

Whether a switch, bridge or router, each device type plays an important role in keeping your IT operations going while the end user is none the wiser. At times, they may seem to overlap in functionality, but the few key distinctions make it so that each layer is only processing the data it needs to, keeping things running smoothly on WANs and LANs alike.

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