Figure 2 Back panel of Linksys wireless router.
Revised: August 26, 2005
By Richard G. Baldwin
File: FwlProj040.htm
This laboratory project was prepared specifically for the benefit of my students who are enrolled in ITNW 1351, Fundamentals of Wireless LANs.
The project was designed under the assumption that students enrolled in the course have successfully completed the prerequisite course, ITNW 1325, Fundamentals of Networking Technologies.
The project design also assumes that the students are actively studying the material in the prescribed textbook for this course, which explains such complex topics as the IEEE 802.11g wireless specification.
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I recommend that you open another copy of this document in a separate browser window so that you can easily view the discussion and the figures at the same time.
The purpose of this project is to show you how to add Internet access to a wireless LAN.
The following equipment is required to complete this laboratory project:
What is a MAC address?
Later in this project, you will be dealing with something called a MAC address.
Therefore, it will be useful to tell you what a MAC address is at this point so that you will have that knowledge when you reach the point in the project where you need to know.
According to Webopedia, the term MAC address is:
"Short for Media Access Control address, a hardware address that uniquely identifies each node of a network. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI Reference Model is divided into two sublayers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The MAC layer interfaces directly with the network medium. Consequently, each different type of network medium requires a different MAC layer."
Wikipedia has this to say about a MAC address:
"In computer networking a media access control address (MAC address) is a unique identifier attached to most forms of networking equipment. Most layer 2 network protocols use one of three numbering spaces managed by the IEEE: MAC-48, EUI-48, and EUI-64, which are designed to be globally unique.)"
Finally, another very useful article on MAC addresses can be found at About.com.
How to find your computer's MAC address or addresses
For Windows NT, Windows 2000, and Windows XP, run the following
command from the command prompt:ipconfig/all
This should
produce an output similar to that shown in Figure 1.
C:\jnk>ipconfig/all Windows IP Configuration Host Name . . . . . . . . . . . . : ABC123456789 Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No DNS Suffix Search List. . . . . . : Belkin Ethernet adapter Wireless Network Connection: Connection-specific DNS Suffix . : Belkin Description . . . . . . . . . . . : Belkin Wireless 54Mbps Desktop Adapter Physical Address. . . . . . . . . : 00-11-22-33-44-55 Dhcp Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes IP Address. . . . . . . . . . . . : 192.168.1.100 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.1.1 DHCP Server . . . . . . . . . . . : 192.168.1.1 DNS Servers . . . . . . . . . . . : 192.168.2.1 Lease Obtained. . . . . . . . . . : Friday, July 22, 2005 4:32:23 AM Lease Expires . . . . . . . . . . : Saturday, July 23, 2005 4:32:23 AM Ethernet adapter Local Area Connection: Media State . . . . . . . . . . . : Media disconnected Description . . . . . . . . . . . : National Semiconductor Corp. DP83815 /816 10/100 MacPhyter PCI Adapter Physical Address. . . . . . . . . : 00-11-AB-CD-EF-12 Figure 1 Typical MAC addresses |
Representative of my laptop computer
The output shown in Figure 1 is representative of my laptop computer at the time of this writing.
At this time, I have two network adapters installed in my computers. One is a Belkin wireless adapter that plugs into a slot on the side of the computer.The other is a wired adapter that is built into the computer.
The wired adapter is disconnected
There is currently no cable plugged into the wired adapter. Therefore, Figure 1 shows that the state of the wired adapter is Media disconnected.
The wireless adapter is connected via RF
I currently have a wireless connection to a Linksys router, which in turn is connected by cable to a Belkin router, which in turn is connected to a cable modem. Hence Figure 1 describes several of the particulars regarding that connection, such as the fact that my computer currently has an IP address of 192.168.1.100.
Two MAC addresses
The two physical addresses shown in boldface in Figure 1 are representative of the MAC addresses of these two networking components.
Later on, you will learn how to view the (apparent) MAC address of the Linksys router.
Just what you have been waiting for
This may be the project that you have been waiting for. This project will show you how to connect your wireless LAN to the Internet.
Effort is almost trivial
After having worked your way through the previous laboratory projects, you will probably find the effort required to complete this project to be almost trivial.
Connecting to a wired network
If you have successfully completed the previous projects in this series, you are going to see that as a minimum, all that is necessary to connect your wireless network to the Internet is:
Connecting to a broadband cable modem
In the event that you are connecting your Linksys router to a broadband cable modem, it may also be necessary for you to either:
A cable that provides Internet access
It is assumed that you have access to one end of a cable that provides Internet access. The other end of that cable could be connected to a number of different devices such as:
Can probably use Linksys factory settings
Assuming that you have access to such a cable, providing Internet access to your wireless LAN will probably be fairly easy.
If the characteristics of the available Internet access mechanism match the default factory configuration settings of your Linksys router, it should be very easy to provide Internet access to your wireless LAN. Furthermore, there is a high probability that this is the case.
Connecting by cable to a Belkin router
For example, I personally use a Belkin 54g wireless router at my house with the Internet signal being fed to the router by a cable modem provided by a commercial cable company (ISP).
By using the factory default settings for the Linksys router (except for having created an encryption password), I was able to connect an RJ-45 cable from one of the wired output connectors on the Belkin router to the Internet connector on the back panel of a Linksys router (see Figure 2) and gain immediate wireless access to the Internet via the Linksys router.
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Address conflicts are possible
The default IP address for the Belkin router was 192.168.2.1 and the default IP address for the Linksys router was 192.168.1.1. Therefore, I did not encounter an IP address conflict.
However, if the two routers had used the same default IP address, it would have been necessary for me to change the IP address of one of them.
Linksys explains how to do this in the User's Guide for the Linksys router.
Connecting to a cable modem
Perhaps more importantly, I was able to remove the Belkin router completely and replace it with the Linksys router by making one critical change to the factory settings for the Linksys router.
Cloning a MAC address for the Linksys router
In addition to establishing an encryption password, (which is not required but is highly recommended), it was necessary for me to cause the Linksys router to clone the MAC address that was being used by the Belkin router.
(The fact that I cloned an existing MAC address instead of registering the Linksys router's actual MAC address with the cable company is the reason that I referred to the apparent MAC address for the Linksys router earlier.)
My cable company requires a MAC address
I don't remember much about the installation of the cable modem several years ago. However, the cable modem is apparently only willing to communicate with a computer (or similar network device) having a MAC address that matches the MAC address of the computer that was originally connected to the cable modem when the Internet access service was first installed.
(It is probably possible to call the cable company and get them to register a different MAC address. One source suggests that it may only be necessary to cycle the power on the cable modem to cause it to reboot and recognize the MAC address of the newly-connected device. However, it is not necessary to do either when connecting the Linksys router because it can be configured to present any MAC address that you want to present to the cable modem. Just configure it to clone the MAC address of the device that it is replacing.)
Other information may be required
Apparently some ISPs require other information, such as host name and domain name to be registered in addition to, or as an alternative to, the MAC address. At least, the Linksys router makes provisions for that possibility. That is not the case with my ISP, so I just left those fields blank in the Basic Setup section of the administrator panel for the Linksys router.
Getting and saving the old MAC address
Before replacing the Belkin router with the Linksys router, I used the administrator panel for the Belkin router to get and save the MAC address that was being presented to the cable modem by the Belkin router.
Cloning the MAC address
Figure 3 shows a screen shot of the page on the Linksys administrator panel that is used to either:
If the computer is currently connected to the cable modem and your plan is to replace the computer with the Linksys router, you can simply click the button that reads Clone Your PC's MAC. That will cause the router to get and save the MAC address of the computer.
Replacing one router with a different router
In my case, I wasn't replacing a computer with a router. Rather, I was replacing a Belkin router with a Linksys router.
I manually entered the MAC address that was previously being used by the Belkin router and then clicked the Save Settings button. That caused the cable modem to recognize the Linksys router as if it were the Belkin router and from that point forward I had wireless access to the Internet.
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Connecting to a wired network
As a third experiment, I connected an RJ-45 cable between the Internet connector on the back panel of the Linksys router shown in Figure 2 and an RJ-45 cable connector on the wall in an office where a computer is normally connected. This gave me immediate wireless access to the Internet. For this experiment, I was using the factory default settings of the Linksys router except that I had implemented WEP encryption.
(This could have resulted in access problems due to address conflicts, but it didn't.)
The project instructions for gaining wireless Internet access are fairly straightforward in most cases.
Connecting to a wired network with DHCP
Assuming that you have access to a wired network that provides Internet access and also assigns IP addresses using Dynamic Host Configuration Protocol (DHCP) to the computers connected to the network, you can probably gain wireless Internet access simply by disconnecting the RJ-45 cable from the back of your computer and connecting it instead to the Internet connector shown in Figure 2.
Under that circumstance, you can probably use the Linksys factory settings and it probably won't be necessary for you to reconfigure the Linksys router in any way.
(However, it would be a good idea for you top at least implement 128-bit WEP encryption on the router to provide some degree of security.)
Configuring for Static IP
If the network that serves as your source for Internet access doesn't assign IP addresses, you will probably need to select "Static IP" in place of "Automatic Configuration - DHCP" as shown Figure 4. You will probably need to make some other associated changes as well.
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(Since I don't have access to an Internet source that assigns Static IP addresses, I haven't been able to experiment with this option as of this writing. Note that there are several other options in addition to DHCP and Static IP, each of which serves a fairly specialized purpose.)
Instructions for a cable modem
Assuming that you will be getting Internet access via a broadband cable modem or DSL modem, you will probably need to modify the factory default settings of the Linksys router by cloning the MAC address as described earlier.
It may also be necessary for you to provide a Host Name and/or Domain Name, depending on the requirements of your ISP. You will need to determine exactly what your ISP requires.
(Once again, it would be a good idea for you to at least implement 128-bit WEP encryption on the Linksys router.)
Making the connection
Having cloned the MAC address, disconnect the RJ-45 cable that connects your computer to the cable modem and reconnect that cable between the modem and the Internet connector on the back panel of the Linksys router as shown in Figure 2.
Kids, do try this at home!
That's about all there is to it. If you have a laptop computer and a broadband cable modem, you may want to try this at home.
I am currently sitting in my recliner, with my feet up, writing this lab project. My cable modem and the wireless router are on the other side of the room.
I have been extremely happy with my wireless router, particularly since it cost me very little after getting rebates on both the router and the wireless notebook adapter.
Now, the next thing that I need to purchase and install is a wireless node for my printer. Then I could print without having to get out of my recliner.
Copyright 2005, Richard G. Baldwin. Reproduction in whole or in part in any form or medium without express written permission from Richard Baldwin is prohibited.
Richard has participated in numerous consulting projects and he frequently provides onsite training at the high-tech companies located in and around Austin, Texas. He is the author of Baldwin's Programming Tutorials, which have gained a worldwide following among experienced and aspiring programmers. He has also published articles in JavaPro magazine.
In addition to his programming expertise, Richard has many years of practical experience in Digital Signal Processing (DSP). His first job after he earned his Bachelor's degree was doing DSP in the Seismic Research Department of Texas Instruments. (TI is still a world leader in DSP.) In the following years, he applied his programming and DSP expertise to other interesting areas including sonar and underwater acoustics.
Richard holds an MSEE degree from Southern Methodist University and has many years of experience in the application of computer technology to real-world problems.
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Figure 3 Causing the Linksys router to clone a
MAC address.
Figure 4 Linksys Basic Setup panel.