How to…Set Up a SOHO Network

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The need and ability to work from home has increased dramatically in the past few years. With lower prices on high-speed Internet and networking equipment, many people are discovering that building and maintaining a small office/home office (SOHO) network isn’t as difficult as it used to be.

The SOHO network solves many of the problems of owning multiple PCs, such as sharing information between users and having an affordable way to get many computers onto one Internet connection.

Requirements
Let’s discuss some of the components needed in order to build a SOHO network. The foundation of the network is its central connecting device, which can be a hub, switch or router. Switches and hubs aren’t as useful in the SOHO environment because they aren’t smart enough to look at the IP addresses of our internal computers. Routers will provide this functionality and some additional functions that will be required to set up the network. The routers that are primarily used for small environments are considered all-in-one devices because they include many features, such as dynamic host configuration protocol (DHCP), network address translation (NAT) and a firewall. There are a few popular brands of small network routers like Linksys, Dlink and Netgear. The example presented here uses a Linksys 4-port broadband router.

You also will need a network card in each of your computers. This can be purchased separately, but most computers come with them built in. To connect your computers to your router, you will need network cabling. You can purchase CAT5 (100 Mbps) or CAT5e (1,000 Mbps) pre-built, or make it yourself. In order to get the 1,000 Mbps data transfer rate, your router and network cards must support it. The final piece of hardware is the modem that will connect your router to the Internet. The modem will most likely come from your ISP. The operating system can be just about anything you like, such as any Microsoft Windows product, Linux or Mac OS X.

Concept
When a single computer talks on the Internet, you have two numbers that serve to identify you, both locally, as well as on the Internet. The first, your Media Access Control (MAC), is permanently assigned to any device with networking capabilities, such as your network card. This cannot be changed (normally) and is used by local network devices to identify you. The second number is your IP address. This is used by computers on the Internet for tracking and sending data back to you. There are two types of IP addresses: routable and non-routable. Although both can be used by routers, this means that some IP addresses can be used on the Internet (routable) and some cannot (non-routable). Your routable IP address will most likely be automatically assigned to your modem by your ISP. We use non-routable IP addresses on our internal network. Your computer also uses ports to tell the remote computer what application you want to communicate with. For example, port 80 is Web traffic (HTTP).

In Figure 1, notice the modem is copying the IP and MAC of the computer. That’s because the modem is representing the computer on the Internet. The modem copies the network card MAC, stopping you from swapping computers on the modem. It will only talk to 0101010101aa.

Putting the Network Together
Let’s get started assembling the network components. You will connect the modem to the router using a network cable, usually CAT5. The router should have an RJ45 port that is labeled WAN or modem—this is the port that connects to the modem. On the Linksys router, there are four ports available to connect computers to, and one port labeled WAN. You also will use network cabling to connect the computer’s network cards to the router. That’s all you need to do as far as components are concerned.

Configuration
Your router will most likely come with a CD that will automatically configure your network for you. This doesn’t always work, so we will discuss manually configuring it.

Since your modem was copying your computer’s MAC address, it might be a bit confused when it is no longer connected to your computer. Your router has an interface that allows you to connect to it and change settings. Simply open the Web browser and type in the IP address of your router. Most routers use default addresses in the range of 192.168.x.x. (This is found in the documentation with the router.)

The documentation that came with the router also should tell you what the default username and password will be. Once logged in, there will be several options available to you. The router needs to be able to copy your computer’s MAC address. There will be a configuration option for MAC cloning. To find out what the MAC of your computer is, simply click START>RUN and type in CMD. This will open the command prompt (Windows XP). Type in “ipconfig –all,” and under “physical address,” your MAC will be listed. Simply copy the 12-digit code into the MAC configuration screen of your router.

Your router also will support DHCP. This will allow the router to automatically assign internal IP addresses to your computers. You can check to see if your computers are getting their addresses from DHCP by getting back to the command prompt and typing the same command listed above. It should state that DHCP is enabled, and your IP address should be similar to 192.168.x.x. If not, there is a configuration screen on the router that will allow you turn on DHCP.

Post-Configuration
At some point, you may want to use a program on the Internet that requires someone to connect to your computer. For example, let’s say I want to connect to my home computer using telnet. The telnet program allows me to connect to a computer on port 23 from anywhere on the Internet and use the command prompt. Most routers will have all incoming traffic blocked—this is a feature of the firewall. Also, because you are using the NAT service, the router must know which computer to send the request to.

Note: Network address translation simply converts several internal (non-routable) IP addresses to a single external (routable) Internet IP address.

You have the ability to enable “port forwarding.” This allows you to configure the router to allow incoming traffic on certain ports to be redirected to a particular computer on your internal network. You must specify the internal IP address of the computer you wish to connect to and the port that the service will use.

In the example in Figure 2, the router would check the configuration for port forwarding. It might find that traffic inbound for port 23 should be redirected to 192.168.1.3. All traffic with that port will be forwarded to the internal computer. Be careful when using port forwarding, because the router will accept connections from anyone, not just you.

File Sharing
You also might want to share data with the users in your local network. Once your router is configured correctly, this should be an easy task. Simply enable sharing on a folder somewhere on your computer by right-clicking on the folder and choosing “Properties.” (This may differ slightly depending on your OS.) With the Properties dialog box open, there should be a tab labeled “Sharing.” The sharing tab will either have a check-box or a button that will enable sharing for that folder and its contents.

Once you have enabled Sharing, you can connect to the share using one of two methods. You can go to START>RUN and type in the name of the computer, preceded by two back-slashes (\computername) and press Enter. It may open a logon box. If so, you will have to type in the username and password that were created for the computer you are connecting to. After the authentication, you will see a list of folders. Among that list shou

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