Computer networking using wireless network

wireless computer networking tutorial and what is wireless computer networking
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HalfoedGibbs,United Kingdom,Professional
Published Date:02-08-2017
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Working Without Wires I wish I could hook up to the Internet without connecting these wires all the time... Surfing the Internet without wires is great This chapter will show you all the things that you need to think when setting up a wireless access point. First you need to consider the physical location, because radio waves can be blocked. Second, we introduce some more network acronyms, NAT and DHCP. But don’t worry, we’ll explain them, so at the end of the chapter you will be able to have one great wireless network up and running. Download at we love starbuzz Your new gig at Starbuzz Coffee Starbuzz Coffee has made a name for itself as the fastest growing coffee shop around. If you’ve seen one on your local corner, look across the street; you’ll see another one. The Starbuzz CEO has a great idea for enticing new customers into his coffee shops. He’ll offer free in-store Internet access to all Starbuzz customers. It’s perfect. People will come in to surf the Internet, and they’ll order more coffee while they’re here. But I don’t want any ugly cables about the place. We’re going wireless Starbuzz Coffee needs a wireless hotspot What the CEO needs is an open wireless access point that his customers can use to access the Internet. In other words, he needs a wireless hotspot. His customers will be able to bring their laptops along to his coffee shops and get an automatic connection to the Internet. What’s more, the back office staff will be able to access it too. So how do we set up a wireless access point? 364 Chapter 10 Download at Boykma.ComSignal travels from the laptop to the AP. wireless networking Wireless access points create networks using radio waves Let’s start by looking at how wireless access points work. When you use a wireless access point to create a network, computers are connected through radio waves instead of Ethernet cables. The access point itself has to have a wired network Laptop with Wireless connection, but all other devices link into it wirelessly. So if you Network Capability have a wireless network capable laptop, you’re free to roam, just as long as you’re in range. Laptop with Wireless Network Capability A big caveat with wireless networks is Wireless Access Point that the radio waves can be blocked or interfered with and have Network Switch limited range. So how do we install a wireless access point? you are here 4 365 Download at Boykma.Com The AP sends signals to the laptop. Ethernet cable connecting AP and switch The wireless capable laptop can receive and transmit radio signals. If your access point has a WAN port and LAN ports, plug the network connection to the WAN port. USB for a printer Plug the security cord in here. The power cord goes here. wireless access points up close Let’s fit the wireless access point Physically fitting a wireless access point is actually pretty simple. Once you have you have your wireless access point device, just take it out of the box, put it somewhere nice and safe where the radio waves can’t get blocked, and hook it up to your network. Here’s what a typical wireless access point looks like: So where should we put the Starbuzz Coffee wireless access point? Take a look round your house or workplace. What sorts of things can you see that might get in the way of a wireless network? What other devices might interfere with it? 366 Chapter 10 Download at Boykma.Com Your network cable plugs into the WAN port here. This particular access point can act like a network switch through these LAN ports.wireless networking Here’s a floor plan of one of the Starbuzz Coffee shops. Where would you put the access point? Draw in where you think the best position for it is. Full height metal stud wall Network switch Customer area Office area Customer area Messy counters you are here 4 367 Download at Boykma.ComAn access point placed on a shelf will give all the customers access, plus the back office. The only real challenge will be running the network cable to here from the switch. where’s the wap? Here’s a floor plan of one of the Starbuzz Coffee shops. Where would you put the access point? Draw in where you think the best position for it is. Full height metal stud wall Network switch Customer area Office area Customer area Messy counters 368 Chapter 10 Download at Boykma.Com This wall could cause some problems with the radio signals.wireless networking Q: Q: Q: So a 802.11G wireless card in, say, Can a single access point talk to Are inexpensive access points a laptop can only talk to an 802.11G different wireless clients with different just as good as the expensive ones? access point? standards? A: Depends. If the features are the A: Yes, but most wireless cards and A: Most of the time this is true. Many same, then you really have to look at built-in wireless interfaces can access access points can “speak” different the quality of the components. They are multiple types of access points. wireless standards at the same time. Many inexpensive for a reason. Many of the times you can turn this off because usage more expensive access points have of older wireless standards can slow down additional features such as printer and Q: Why are there old access points the new standards. external hard drive support. that don’t support newer protocols around still? Q: Q: Can one brand of wireless card, Why would you connect a hard say a Dell, connect to an access point of drive to an access point? A: Because someone invested money another company, like Apple? in them and does not want to spend the money to replace them. A: An access point with an external hard A: Yes, as long as they are using drive attached to it provides a Network the same wireless standard, they will Attached Storage unit. Anyone with communicate together fine. wireless access can store file on that hard drive. you are here 4 369 Download at Boykma.Comnot so fast... Test Drive The wireless access point’s all hooked up, so let’s put it to the test. Let’s try connecting a computer to it and see what happens. 1 Turn on the wireless networking on the computer. In some older machines, this may have to be installed. But most modern operating systems have wireless ready to go. 2 Connect to the access point. Essentially you should see a list of access points; select yours from the list to attach to it. 3 Enter any password required. Most access points have some type of security. Most of the time it is a password that you have to enter when you attach to the access point. 4 Test your connection. At this point you should be able to access network resources such as the Internet via the access point. So is the wireless hotspot working okay? You’re kidding me, right? I can’t get to any websites, not even starbuzzcoffee.com. How will my customers be able to surf? So what went wrong? 370 Chapter 10 Download at Boykma.Comwireless networking Why doesn’t the wireless hotspot work? Based on the results, write down some things that you think may be going wrong. The laptop has a great wireless connection. A ping just returns nothing or some errors. There are green LEDs on the switch and the access point where the Ethernet cables is connected. What could be wrong? you are here 4 371 Download at Boykma.Comtroubleshoot your wireless Why doesn’t the wireless hotspot work? Based on the results, write down some things that you think may be going wrong. The laptop has a great wireless connection. A ping just returns nothing or some errors. There are green LEDs on the switch and the access point where the Ethernet cables is connected. What could be wrong? Is the Ethernet cable plugged into the WAN port on the access point? Is the problem bigger? Can computers hooked to the switch by Ethernet get on the network? Is the access point configured with the correct IP address information? Is the access point configured to give out addresses correctly? 372 Chapter 10 Download at Boykma.Comwireless networking What about the network configuration? When we set up a wireless access point, it’s not enough to just plug it in. We need to say which computers can use the wireless access point. You’re kidding me, right? You mean we have to tell the wireless access point which computers can use it? But that’s all the Starbuzz customers Why can’t they just show up and use it? Maybe she has a point. The last thing you want to have to do is manually setup an IP address for every Starbuzz customer that walks into the shop. So what can we do? Fortunately, there’s a way round this, and it’s called DHCP. you are here 4 373 Download at Boykma.Comenter dhcp So what’s DHCP? DHCP stands for Dynamic Host Configuration Protocol. It’s a way of automatically allowing devices onto your network with no manual intervention on your part. Here’s how it works. 1 DHCP Discovery. The client broadcasts to find available servers. To do this, it needs an IP address network interface configured to use DHCP. Hey, are there any DHCP servers listening out there? Helloooooo 2 DHCP Offers. The DHCP server in the wireless access point responds to the client broadcast by offering the client an IP address. The IP address is within a pre-defined range that the DHCP server has configured in its pool of available addresses. I’m over here Would you like to use this IP address? 374 Chapter 10 Download at Boykma.Comwireless networking 3 DHCP Requests. The client broadcasts a DHCP request message, accepting the offer of the DHCP server. Ah, there you are Yes please. 4 DHCP Acknowledgement. The DHCP server sends a DHCPACK packet to the client. The packet gives the client the length of time it can hold and address (lease duration), and any other configuration details that are needed. In that case, it’s yours for the next half hour. Enjoy DHCP allocates IP addresses DHCP makes our life easy by offering to clients IP addresses it has in its pool of available addresses. This sounds like just the sort of thing that Starbuzz Coffee needs, as it means clients will be able to come into the store, open up their laptops, and start surfing. So how do we set up DHCP? you are here 4 375 Download at Boykma.Coma little setup First make sure the client has DHCP turned on... A wireless access You configure this in the client’s network configuration. point may come with the DHCP service turned on by default. Windows Mac OS X Linux (Ubuntu) Second, make the wireless access point a DHCP server... The first thing we need to do is turn on the DHCP service on the wireless access point. This tells the wireless access point that you want it to be a DHCP server. The wireless access point may come with DHCP switched on by default, but in case it doesn’t, here are the settings you need to change. 376 Chapter 10 Download at Boykma.Com This means DHCP.A typical DHCP setup screen on an access point. wireless networking ...and then specify an acceptable range of IP addresses After you’ve told the wireless access point you want it to be a DHCP, you need to tell it which IP address ranges to give out. You also configure information such as the gateway and DNS name server addresses, and how long the client can keep hold of the IP address for. 208.62.154.2 208.62.154.8 Q: Q: Q: What happens if there is more Can I control which machines get Can the IP addresses my DHCP than 1 DHCP server on the network? which IP addresses? host gives out be public IP addresses? A: The client responds with a broadcast A: Yes, you can put into a special table A: Yes. Just make sure that no other DHCP request. That broadcast contains the the MAC addresses of those machines and machine is using them and that they are specific information from 1 DHCP server, so what IP addresses they should be issued. routable. it is the only one that does anything with the request. So the protocol is written with Q: Q: What happens when a DHCP host How long do clients get to keep an multple DHCP servers in mind. runs out of IP addresses? IP address? Q: Does a Windows client have to use A: Good question. It just stops A: That is called the lease. It is for a Windows DHCP server? responding to any discovery broadcasts whatever time you set it for. Typically it is a until some addresses free up. couple of hours to days. A: No. As long as the DHCP server meets the protocol standards, it will work fine with a Windows, Mac or Linux client, or even some other device looking for an IP address with DHCP. you are here 4 377 Download at Boykma.Com The gateway and DNS are set in different places depending on the particular DHCP server. This is how long a client can keep an IP address before it has to request a new one. You need to setup a pool of IP addresses that the DHCP server can give out.dhcp exposed The DHCP Server Exposed This week’s interview: Secrets of the DHCP Server Head First: Hello. DHCP Server: Once in a while. The admin has a pretty good number of IP addresses in the pool. It DHCP Server: Hello, here is an IP address: meets the demand. 192.168.100.1, with a gateway of... Head First: Do the clients get mad when they get Head First: Hold on a second What is all this? denied? DHCP Server: Oh sorry, I don’t normally get into DHCP Server: No, they just sit and keep trying conversations outside of work. and trying. Head First: So you work pretty hard? Head First: Don’t they get mad at you? DHCP Server: Man, it is just request after request DHCP Server: I don’t offer anything to them, after request. It never ends. It seems just as I give a so they do not know that I am around. I keep my client an IP address, they are back for another one. mouth shut until I have some addresses available. Head First Server: Wow, it sounds like your lease Head First: That sounds like a smart thing to do. time is set too low. Well thank you for the interview, and we hope you DHCP Server: Yea, that is what I think, but I really get some time off soon. have no way of letting the network administrator know that other than logging it. Head First: Let’s hope she checks the logs once in a while. So do you ever deny a request for an IP address? So has setting up DHCP solved Geek Bits the problem? The connection works Before too long, the wireless You can read more about DHCP by reading access point is live, and people start flocking in even the RFC located at greater numbers to the Starbuzz Coffee shops. http://www.faqs.org/rfcs/rfc2131.html 378 Chapter 10 Download at Boykma.Comwireless networking This time it’s personal Things were going fine until one particularly busy day in the coffee shop... Where’s my internet connection, baby? I came in here to surf MeBay, and can I get there? No Everyone else seems OK, so what’s going on? Why are you doing this to me? Uh-oh Everyone who came into the coffee shop before this guy is happily surfing the Internet. The trouble is, everyone who came in afterwards can’t get a connection. Why do you think the wireless access point won’t let any new clients connect to the Internet? Hint: Look back through the DHCP configuration for clues. you are here 4 379 Download at Boykma.Com Wow... maybe too much coffee can be a bad thing.out of ips We’ve run out of IP addresses Can you remember when we set DHCP up on the wireless access point? We configured a range of IP addresses that the DHCP server could allocate to clients. Our ISP only gave us 12 IP addresses and the other 5 are being used by other computers on Ethernet. 208.62.154.2 208.62.154.8 But what happens when we have more clients than available IP addresses? The DHCP server can only give out a limited range of IP addresses, and when it runs out, that’s it. It can’t offer any new clients a connection. So what can we do to get around this? So it gives up? But that’s ridiculous. There’s gotta be a way around this, right? We can get around the IP address problem by implementing NAT. NAT stands for Network Address Translation, and it’s something else we can enable on the wireless access point. With NAT enabled, we can use just about any IP address we want, and however many we need to. So how does NAT work? 380 Chapter 10 Download at Boykma.Com This is the available range of IP addresses.wireless networking NAT works by reallocating IP addresses Here’s what happens when a client accesses a website using NAT. 1 The client sends a packet to the wireless access point. In this case, it uses 192.168.1.1 for the source IP address on the packets. 192.168.1.1 2 The access point sends the packet on to the web server. But it changes the packet’s source IP address to a public IP address such as 204.62.201.18, and records it in a table of inside addresses translated to outside communication streams. 192.168.1.1 204.62.201.18 3 The web server responds. It sends the requested information to the public IP address 204.62.201.18. 204.62.201.18 192.168.1.1 204.62.201.18 4 The access point forwards the traffic to the client. But it changes the destination IP address of the packets back to the private 192.168.1.1 by checking its translation table. 192.168.1.1 204.62.201.18 192.168.1.1 204.62.201.18 you are here 4 381 Download at Boykma.Com An Internet web server Each brand of access point has its own interface for doing this. The concepts are the same, but the interface may look different. just turn nat on So how do we configure NAT? Configuring Let’s set up NAT on the Starbuzz wireless access point. Wireless access NAT on most points sometimes come with NAT switched on by default, but in case yours doesn’t, here’s the setting you need to change: access points consists of turning it on, and that’s about it. 382 Chapter 10 Download at Boykma.Com