Networks for Home/Small Business

[Rob Pomeroy]

Contents

1. Intro
2. Dial-up internet connection
3. (DSL/Broadband/Cable) Modem connected to a single PC
4. (DSL/Broadband/Cable) Router networked to all PCs
5. File and print sharing

1. Intro

Your goal: Connect together computers on a home or small business network.  Share an internet connection.  Possibly also share files and printers across the network.  You don't need much knowledge in order to achieve this, but a little bit of understanding will help.

You can skip the intro and use one of the links above to find the information you particularly need, if you're impatient. 

O Computer, Where Art Thou?

In order to talk to each other, computers need to know where other computers are.  If you want to talk to another person, you need that person's telephone number.  A similar principle applies to networking computers.  The number that computers need to know is called a TCP/IP address.  TCP/IP addresses (or just "IP addresses" for short) look like this:

192.168.1.1
248.2.98.3
48.7.2.11
10.0.0.2

That's four numbers separated by dots.  Each number can be from 0 to 255.

Talking the same language

TCP/IP is the system that most networked computers use to talk to one another.  It has been around for a long time and has become the de facto international standard.  There are other networking languages (called protocols), but you do not need to worry about them, since you will only be configuring TCP/IP.

Commonly some computers will have more than one network protocol installed.  IPX/SPX is often in the list of installed protocols.  For our purposes, all extraneous protocols should be removed, in order to avoid conflicts, and to keep things as streamlined as possible.

Limitations

The obvious limitation with IP addresses is that we can easily run out of numbers.  The maximum number of computers that could be addressed would be 255 x 255 x 255 x 255 = 4,228,250,625.  At one time, it was inconceivable that there would be over 4 billion computers in the world, but we easily hit that limit today.

Private Subnets
To overcome this problem, several ranges of IP address are reserved for private use.  In other words, these addresses will only ever be seen on a private network, and should never leak out onto the wider internet.  These are the Class A, B & C networks, as follows:

A
There is one possible Class A network
IP address range = 10.0.0.0 - 10.255.255.255
Subnet mask = 255.0.0.0

B
There are 16 possible Class B networks
For one network: IP address range = 172.x.0.0 - 172.x.255.255
where 'x' is a number from 16 to 31
Subnet mask = 255.255.0.0

C
There are 256 possible Class C networks
For one network: IP address range = 192.168.x.0 - 192.168.x.255
where 'x' is a number from 0 to 255
Subnet mask = 255.255.255.0

The "subnet mask" is a number that we can use along with a clever bit of binary arithmetic, to ensure that we are talking to computers within the appropriate address range.

This whole system may be phased out in time, replaced by a system with much more logical capacity.

What Does This Mean To You?
Simply put, the computers on your private network (your "LAN" - local area network) will use addresses from one of the Class A, B or C networks - probably, but not necessarily, a Class C (e.g. 192.168.1.x).  Then your entire LAN will have one IP address, assigned by your ISP (Internet Service Provider).

Losing track

For people running a network with lots of computers, it can be hard to keep track of all the IP addresses that have been assisgned - especially when computers get moved around.  Instead, you can use a system called DHCP (Dynamic Host Configuration Protocol).

It sounds complicated but it boils down to this: a new computer enters a network, with no IP address assigned.  It yells 'Is there a DHCP server here?  I need an address!'  The DHCP server replies, 'Yes, I'm here, and here is your address for this session.'  The DHCP server tracks the IP addresses it has assigned and ensures that there are no conflicts on the network.  Only one DHCP server should run on a subnet.  Many broadband modem/routers have a built in DHCP server.

So DHCP sounds great - but it has its drawbacks.  You may need to know where a certain computer is at all times - eg a web server on your local network.  You would have to assign that computer an IP address manually, and ensure that any DHCP server is told not to give the address out to anyone else.

In practice, in smaller networks (less than ten computers) it can be easiest to assign all IP addresses manually.  For home/small business, that is my recommendation.

[Rob Pomeroy]

Contents

1. Intro
2. Dial-up internet connection
3. (DSL/Broadband/Cable) Modem connected to a single PC
4. (DSL/Broadband/Cable) Router networked to all PCs
5. File and print sharing

2. Dial-up internet connection

Dial-up internet connections (e.g. using an analogue modem) are usually too slow to be used by more than one computer at a time.  If you are considering attempting to share such a connection, let me warn you away from it immediately.  You should only consider this if your dial-up connection is always on and/or free.  The instructions for (DSL/Broadband/Cable) Modem connected to a single PC will apply to you.

[Rob Pomeroy]

Contents

1. Intro
2. Dial-up internet connection
3. (DSL/Broadband/Cable) Modem connected to a single PC
4. (DSL/Broadband/Cable) Router networked to all PCs
5. File and print sharing

3. (DSL/Broadband/Cable) Modem connected to a single PC

In this scenario, you typically have a cable or broadband modem which connects to your (main) computer by USB.  If the modem doesn't have built in ethernet ports, you will need to use Internet Connection Sharing.  (If the modem does have ethernet ports, read the next message in this thread instead.)

If we're looking at a wired network, you will need: 1 ethernet card per PC (preferably one that can run at 100Mbps - most can now), one hub (if you're networking more than 2 PCs) and one ordinary category 5, 5e or 6 network cable per PC to connect from the ethernet ports to the hub.  Alternatively, if you're just networking two PCs, you can do without the hub and just use a single "crossover" cable going directly from one PC to the other.  See the following two diagrams:





Each network point on this network must have an IP address (see the intro).  That is, the modem and each ethernet card.  The IP address for the modem will be assigned by your ISP.  If you have not paid for a static IP address, you may find that your modem's IP address changes every time you connect to the internet.  This is normal.

For all the ethernet cards in your computers, you're going to set up an IP address manually.  The settings, depending on your version of Windows, are found under the Control Panel, in Network, or Network Connections.  In either case, you must find the correct network connection to change.

Windows 95, 98 and ME

Control Panel-->Network

You will see a list of installed software components.  A computer icon indicates a program (typically enabling you to log on); a green card icon indicates a physical network component - any modem will be listed here (as "dial up adapater") along with any network cards; a cable and plug icon indicates a network protocol - the language that will be spoken on the network.

Pay attention to the list of protocols.  If you see IPX/SPX anywhere in that list, click on it and then press "Remove".  You should be left with TCP/IP as the only protocol.  If you have more than one network card/modem, you will see a TCP/IP protocol listed for each of them.

Click on the TCP/IP protocol for your network card, and then click properties.  Set up as follows:

On your main computer (connected to the modem), select "Manually assign IP address".  I recommend using the address 192.168.1.1 here, and the subnet mask 255.255.255.0.  Leave everything else untouched.

On each other computer, select "Manually assign IP address".  Enter the next address for you network - i.e. 192.168.1.2 for PC2, 192.168.1.3 for PC3 and so on.  The subnet mask again is 255.255.255.0.  Additionally, go to the DNS settings in that tab.  There you must enter the IP address of your main computer - 192.168.1.1.  You can enter anything in the domain box - it doesn't really matter.  Finally, under the "Gateway" section, again enter your main PC's IP address, 192.168.1.1.

If you find that these computers can connect to each other, but can't browse the internet (even once you've set up ICS), try changing the IP address for DNS to whatever you ISP says your DNS server should be.  On many versions of Windows (pre XP), you can find this out for yourself: Start-->Run-->winipcfg.  Check the DNS setting shown for your modem.

Windows 2000+

The theory is the same, but the location of the settings is different: Control Panel-->Network Connections.  Right-click on your LAN connection and choose "Properties".  Then follow the general guidelines as for earlier versions of Windows.

Internet Connection Sharing

Finally, you need to enable Internet Connection sharing on your main PC.  This is not available on all versions of Windows.  If you don't have it on any computer on your network, you'll have to bite the bullet and buy a broadband/cable (as appropriate) modem/router and follow the next section instead.

If you have ICS, you can then follow the procedures outlined here, on Annoyances.org, just ignoring the network setup bits that you've already done, following my instructions here.

Caveat: I never use Internet Connection Sharing myself, so have not personally tested the above.  I believe it should work, but am willing to be corrected.

[Rob Pomeroy]

Contents

1. Intro
2. Dial-up internet connection
3. (DSL/Broadband/Cable) Modem connected to a single PC
4. (DSL/Broadband/Cable) Router networked to all PCs
5. File and print sharing

4. (DSL/Broadband/Cable) Router networked to all PCs

This is without doubt the preferred setup when sharing a fast connection with a network.  You do not need to leave any computer switched on; each effectively has its own independent internet connection.  Your router will normally have several network ports and may also have wireless capabilities.  Ideally, the router will have a built in firewall and will be an all-in-one DSL (or cable) modem/router/hub.

For this setup, in addition to the router, you will need: 1 ethernet card per PC (preferably one that can run at 100Mbps - most can now) and one ordinary category 5, 5e or 6 network cable per PC to connect from the ethernet ports to the router.  Thus:



Each computer requires an IP address (see the intro).  Your router may have a built in DHCP server, which makes it possible to set up the network automatically, but you may require more control over it.  If you have any plans to host a web site, gaming server, FTP server, etc, from within your LAN, you will need to assign IP addresses manually.  To do this, see the instructions on manual assignment in the previous section.  You must bear in mind that your router also has an IP address, and your computers and router must all be on the same subnet in order to talk to each other.

By way of example, I own two routers.  One comes configured as 10.0.0.2 as standard.  I therefore selected IP addresses like 10.0.0.3, 10.0.0.77, etc.  The other router comes set up as 192.168.1.1.  This one however I changed to 192.168.77.99, and then used IP addresses for the computers like 192.168.77.1, 192.168.77.66, etc.

Finally, you do not need to use internet connection sharing, for obvious reasons.

[Rob Pomeroy]

Contents

1. Intro
2. Dial-up internet connection
3. (DSL/Broadband/Cable) Modem connected to a single PC
4. (DSL/Broadband/Cable) Router networked to all PCs
5. File and print sharing

5. File and print sharing

Whatever kind of network you have installed, you will probably want to be able to share files around the network, and possibly printers too.  When you don't have a server involved (e.g. Windows 2003 SBS) this is called peer-to-peer file sharing; all PCs have the same status.  This form of file sharing is not especially secure.  Passwords tend to be weak or easy to attack by "brute force" (trying every possible combination).  This is one reaon why you need to have satisfactory firewalling arrangements.  Windows file and print sharing uses ports 137, 138 and 139.  You don't need to know what that means, you just need to make sure that your firewall blocks those ports from the internet!

The easiest way of sharing resources, is to make sure that your computers are all within the same workgroup.  Not a particularly complex concept - you just need to give the computers the same workgroup name, e.g. "HOME", "WORKGROUP" or "OFFICE".  The settings are found in different places depending on which version of Windows you are using.  Before Windows 2000, the setting was in Control Panel-->Network.  From 2000 (I think - never played with 2000 personally!) onwards right-click "My Computer", choose "Properties", then click the "Computer name" tab, followed by the "Change" button.  Ignore anything about domains; you just want to set the workgroup.

You may need to reboot your PCs after changing these settings.  Once done, setting up sharing is as easy as right-clicking the folder/printer you want to share, and clicking "Sharing".  Give the resource a name, change any other options you want to change, and away you go.  You can then browse to those resources from other computers, using "Network Neighborhood".

A note about wireless networks

Currently, all wireless networks can be cracked.  The problem with wireless is that it's indiscriminate.  The signal is scattered, and anyone within range can pick it up.  Contrast that with wired networks, where you need some form of physical access in order to "enter" the network.

Once a wireless network has been detected, it is not difficult for someone with the knowhow to crack the network's encryption.  They then have access to all the resources on your network - and scarily they can do this from an unmarked van parked outside your house.  You may not even be able to detect the intrusion.

For this reason I strongly recommend that you use maximum security if you have a wireless network.  Switch of file and print sharing, unless you're sure you need it.  If you need it, use very strong passwords.  Use software firewalls on all PCs, and it goes without saying, use reputable virus and spyware detection software and keep it up to date.

[Rob Pomeroy]

Right, I think I'm done for now, barring any errors.  dl65 and blackberry, could I ask you to delete those messages of yours?  Only because they're throwing out the links.  Thanks!

Flame: Posts removed, topic locked.