Network Devices – CompTIA A+ 220-801: 2.9

| December 2, 2012


We use many different network devices to connect our devices together. In this video, you’ll learn about hubs, switches, routers, firewalls, and much more.

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Before we had network switching, we used network hubs. It was a very easy way to connect everybody up to a centralized point on the network. And because we were using twisted pair and using the star-based connectivity, it provided us with some advantages over the old coax-based, bus type technologies. One of the disadvantages of hubs is, as more people communicated on the network, the performance of the network degraded for everybody. You didn’t have the separation of communications like you do in modern switch technologies.

You’ll commonly see hubs running at speeds of 10 megabits per second and 100 megabits per second. You don’t see gigabit-based hubs, although it’s part of the gigabit specification. There was never a manufacturer that created gigabit hub technology. And what you’ll find is, hubs are pretty difficult to find these days. It’s a technology that’s not created any longer. And generally, the only people who need to use hubs are people they need to tap into 10 megabit or 100 megabit network connections. So you generally will see these used by network managers or by people who want to use protocol analyzers,

These days, if you’re connecting to a network, you’re probably plugged into a switch. A switch is effectively a multi-port bridge. And all of the decisions about moving data inside of that switch are made in hardware. So it’s very, very fast in how it operates.

If you’re familiar with the OSI model, switches work at OSI layer 2. They are very intelligent about where they’re sending your data. If you recall, with a hub, when traffic went in one port, it was sent to every other port on the hub. Well, it doesn’t work that way on a switch. When traffic is sent into a switch, the switch examines the traffic and only sends the traffic out to the destination port associated with that traffic.

So you can have many different conversations going on inside of a switch, but because of that switching architecture, the increase in connectivity between devices isn’t going to affect the network overall. You now have very specific paths set up between one station and another.

Another advantage of switches is that you can have a central switch with hundreds of ports on it. Because you are intelligently determining where that traffic is going, you don’t suffer the slow down problems that you have when you were using hubs. And these switches support very high bandwidths, not only in the method that it’s using to communicate, but the individual interfaces on the switch as well. You can connect in users at 10/100, or gigabit connectivity and maybe even have 10 gig links that might connect one switch to another.

A router is a device that’s designed to send traffic between IP subnets. And if you’re familiar with the OSI model, this is a device that operates at OSI layer 3. Sometimes you’ll hear people were refer to these as layer 3 switches, but that’s a bit of a misnomer. Switches operates at layer 2. Routers operate at layer 3.

Routers are also very good for connecting different kinds of networks together. So you can connect a Local Area Network to a Wide Area Network or maybe use a fiber-based network, and you’re connecting that to a copper-based network. These generally will be on different IP subnets, so it makes perfect sense to use a router to connect those together.

A term that you’ll hear in larger environments is a Wireless Access Point, or a WAP. This is different than the wireless router than you might have in a soho or a home office. It looks very familiar, but, in reality, it’s not doing routing. It is simply bridging a network that is wired onto a network that is not wired. All of this activity is occurring at OSI layer 2. So we’re not changing the subnet. We’re not routing anything. We’re simply extending the Wired Ethernet Network onto a wireless connection.

When describing switches, we’ve used this term bridging a lot in this presentation. A bridge is a device that connects different networks together at layer 2. It sometimes is used to connect different topologies together, and this is really an old way of communicating between those devices. These days, we’ve taken that idea and incorporated it within switches.

And just like with switches, we’re able to communicate between these networks using the MAC addresses. So if we’re following along in our OSI model, this is an OSI layer 2 device. These days, if you think about bridges, we’re certainly bridging inside of a very large switches. But you can also think of this as the method that’s used in a Wireless Access Point to bridge between a wired ethernet network and the wireless network.

Another network device you commonly see is a modem. That stands for Modulator/Demodulator. And it’s a way to take your digital signals and send them via audio across a type of connection. Sometimes that’s a phone line, sometimes that is a leased line from a network provider. But you’ll need a modem on both sides to make that work. It’s common to see this being used on really standard phone lines. If you have a remote site, and there’s no high speed connectivity to that site, you simply need to transfer small amounts of data, you can use these modems to accomplish this.

Since we have so many choices for high speed internet these days, it’s not really common to see individuals using modems. But if you’re just needing a utility function, you need to transfer a file at the end of the day, you have an automated method to make that happen, or you just need to transfer a small amount of data, you can simply use a modem to make that happen.

Another popular network device is network attached storage. Who doesn’t want to have a lot of storage available right there on the network to be able to use. And of course, not just you can access it. Because it’s on the network, it’s available to be accessed by anybody who might be on your connection. This is usually connected via a high speed connection because you’ve got a lot of data going in and out of this device. Network attached storage isn’t usually using a slow connection like a USB connection.

These network attached storage devices are also designed to grow with your organization. So if you’re storing a lot of data, and you’re realizing that that network attached connection is filling up, you can replace drives inside this device or you can connect multiple of those network attached storage devices together. And one unique capability to this network attached storage is, it’s almost always going to be set up in a redundant and highly available mode.

That way, if you lose one of the drives inside of this connection, it will continue to operate without a problem. And when you have maintenance, you can pull out the bad drive, replace it with a brand new drive while everything continues to run. And it will rebuild itself to get back to 100% operation.

If you’re connecting to the internet from anywhere, you’ve probably got a firewall between you and the rest of the world. These firewalls commonly connect you and filter information based on port numbers. So in the OSI model, we’re really talking about OSI layer 4. Some of the newer types of firewalls will even look at the application that you’re using and filter traffic based on that– something that’s operating at OSI layer 7.

It’s very common to see firewalls being used between one site and another to be able to encrypt the data between those two connections. That capability is usually something that’s built in to many firewalls. These can also often be used to proxy traffic. So you can make your request to the firewall. The firewall makes the request to Google. And the response from Google comes to the firewall, which then examines that and then provides you with that secure data.

Another characteristic of firewalls is that they can commonly operates as a router. So they can operate at OSI layer 3. So sometimes it will sit there, right on the edge of the network, and it will perform IP routing between the inside your network and the internet side of your network.

Historically, we haven’t thought of our phones as network devices. But of course, these days, with a voice over IP, our phones are simply another connection on our existing networks. They act as a normal phone, but there’s so many other capabilities built into this device. You’ve got browsers. There’s multimedia integration. You can connect this to your computer and access it from your computer as well.

Very often, these phones have voice communication inside of them, along with video communication. There might be a camera right on the phone itself. And because you’re on the network with plenty of connectivity and plenty of bandwidth, why not take advantage of some of that speed?

In many organizations, they built applications that run right on the phone itself. So if you need to clock in at the beginning of the day and clock out, you don’t have to go to a box on the wall. You don’t have to log into your computer. You simply go into your phone, and you click a couple of buttons. You can also configure these phones with specialized applications to log in and log out of the phone if you were working in something like a call center.

It’s becoming very common these days to see a lot of this network capability built into a single device. And if you’re a small company or a medium-sized company, it might make sense to find a single device that can be a switch, and a router, and a firewall, and an access point, and have the ability for quality of service, and all of these other functions, built into one machine. That way, you have one place to go to manage the device. You don’t have a lot of different boxes on your network. You don’t have to learn a lot of different environments. You go to one single place to take care of all of your networking needs.

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Category: CompTIA A+ 220-801

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