Networks or networking is quite a large subject. These are the basics which should provide Small and Medium Businesses enough information to run reasonably well.
Basics
Networks work on protocols. These days the vast majority
(including the internet) run on TCP/IP. For computers, printers,
servers etc to communicate with each other, each of these things needs
an IP address. To make things slightly easier, networks usually have
the ability to map a name to this IP address, so the server name might
be "server" instead of "192.168.0.1".
To make this easier to understand, think of this like your home address. You might say "I'm going to Bill's for a beer". Your mate might say, "where the hell does Bill live" and you reply "14 Smith St".
The network only understands IP addresses, you only understand names. So you say to the network "I want to get my file off the "Server" and the network hears "I want to get my file off 192.168.0.1".
DHCP
How does your computer, printer, server whatever get a network address? Good question!
DHCP is the easiest way. Dynamic Host Configuration Protocol (DHCP) hands out IP addresses to anything that requests it. Most things are set so that they request an IP address when they start up. The down side to this, is that your printer or server may get a different IP address every time it starts up and sometimes this causes confusion. DHCP has a way around this by setting reservations. There are other ways around this as well, but we'll stick with reservations for ease of explanations.
MAC or Physical Addresses
Everything on a network has a MAC, which is also known as a
Physical Address. Networks don't actually even use IP addresses, they
use MAC's which are even harder to remember. A MAC is 12 hex characters
long and might be 54-DB-8F-6C-15-6E. So names map to IP addresses and
IP addresses map to MAC's. Confused? Me too!
To simplify things, forget about MAC's. Well sort of. The important thing to remember, is that to reserve an IP address, you need to find out the MAC. This is often called "Physical Address" and is often printed on the exterior of the computer or printer or whatever. If not, then there are ways to find it out. In Windows XP and Server versions, open a cmd prompt (Start > Run >"cmd">Enter) and type in "ipconfig /all". You should see something like "Ethernet adapter Local Area Connection" and in this section will be "Physical Address". If you want to reserve an IP address, then you need to type this Physical Address into the DHCP server, associated with the IP address you want to give it.
It is a good idea to give anything that more than one person connects to, a reserved IP address. This is servers, printers, gateways (ADSL routers) etc. ADSL routers are usually given a static IP address when they are setup and are generally set to be a DHCP server. If you have a Windows Server, this often has a DHCP server on it. The problem with this, is that you can only have one DHCP server on a network, so you may need to decide which one you want to enable and which one you want to disable.
Gateway
Everything needs to know the gateway address if they want to
connect to a network outside of their own. The internet, for example,
is a network outside of your own. Usually the ADSL router will be the
gateway and this will be setup during the ADSL router install, so that
DHCP automatically tells all computers and other things on the network,
what the gateway address is. In most cases, you won't need to do
anything about setting the gateway, but if things can't get to the
internet, this could be the problem.
Routers
Routers connect two networks together. So to get to the
internet, you need a router that connects your network to the internet.
Most ADSL modems are also routers. In most cases, you won't need to do
anything about routers.
Firewalls
Firewalls stop the internet from getting to your network,
but allows your network to get to the internet. Well they do if they
are turned on. Most ADSL modems have a firewall on them and are usually
turned on either by default or when they are setup. You should make
sure that you have a firewall on your ADSL modem. Most operating
systems also have firewalls and you should make sure these are turned
on as well.
Port Forwarding
This is usually a function of a firewall. This allows
something from outside of your network, (usually the internet) to get
to something on the inside of your network. Generally you won't muck
around with this, but if you want remote access to your network, you
will need to setup Port Forwarding to forward the correct port to the
correct piece of network equipment. Common Ports that people might want
forwarded are 80 if you host your own web service, 3389 for Remote
Access, 1723 for PPTP VPN remote access, 21 for FTP.
Switches and Hubs
Hubs have pretty much disappeared and you can't buy them
anymore. This is mostly because, by comparison to switches, they aren't
any good. You still hear the term occassionaly, but people almost
always really mean switches when they say hubs. A switch allows
everything to talk to everything on the network. They are the heart of
the network. Given the cheapness of them now, you are best off buying
one that has many more ports than you need, as you always seem to fill
them up with time. They generally come in 5, 8, 16, 24 and 48 port
sizes for Small and Medium Business needs and have speeds of 10/100 or
Gigabyte. Unless you have large files that you are often accessing from
a central location, 10/100 will be fast enough, but think about going
GB if the cost is not much more. Don't bother paying more for
"management capabilities", you don't need them.
VPN
VPN's are Virtual Private Networks. Which means nothing to
most people. However, they are actually quite useful. What it allows
you to do is connect into your network from anywhere on the internet
and work as if you were in your office. Well almost, it is a bit
slower, depending on your internet connection speed. ADSL modems
sometimes come with the ability to be VPN endpoints (termination
points) or to Port Forward VPN ports. The most common type of VPN is
IPSEC. Which can be difficult to setup. Microsoft use PPTP VPN's, which
are much easier to setup and the type we recommend for Small and
Medium Businesses. Not all ADSL modems support PPTP VPN's from either
the endpoint or Port Forwarding. We recommend that you get one that
will, at the very least, do Port Forwarding of PPTP (Port 1723) if you
think you will ever need a VPN.
VPN's are quite a big subject in their own right and their is quite a lot about them on the internet. If you want to set one up, we recommend doing a bit of googling or getting in someone that can set them up for you.
Remote Desktops
Using Remote Desktop, also referred to as Terminal Services
or RDP (Remote Desktop Protocol) is another way of providing remote
access. This doesn't require a VPN, but may require a Terminal Server
depending on the number of people that want remote access to the
network. With Remote Desktop, you connect to a server or PC on your
network and actually work on that PC or server, rather than on your own
PC. This requires a little more knowledge of how things work if you
want to copy files to your PC where you are, but it can be done
reasonably easily once you understand how it works. To get the hang of
Remote Desktop (RD), it is worth while playing around with it while you
are in the office so you can see how it works.
There are a number of steps you need to do to get things working.
The PC or Server that you want to RD to needs to be setup to allow RD. Only Windows XP Professional version and Windows Server 2000+ have the ability in the Windows OS to accept RD sessions. We will concentrate on XP as that is the easiest. You can Google for articles on Server versions and other OS's such as Linux and Mac.
To enable RD, right click "My Computer" and select "Properties". On the "Remote" tab tick the box under "Remote Desktop" that says "Allow users to connect remotely to this computer and select the "Select Remote Users" box and decide who can connect. Back on your own PC, click on "Start > Run >" and type in "mstsc" and hit enter. You can also get to this under "All Programs > Accessories > Remote Desktop Connection". Microsoft change the Remote Desktop Client all the time, so it will depend on which version you have as to how the next bit works.
Before connecting, select the "Options" tab and have a bit of a look around. The defaults are fine for most things. Click on the "Resources" tab. If you use many keyboard shortcuts, you will want to set this section to "On the remote computer". If you want to print from your own PC, you will need to check the "Printers" setting. If you are rarely or never going to print, then uncheck this box. "Clipboard" you will want to check and "Disk drives" if you want to copy files across RD to your PC. Drives can be found under "More" on some versions.
Type in the computer name of the computer you want to connect to and follow your nose. Spend quite a bit of time connecting with all the various options this before you need to use it, as there are quite a few little things to it that it pays to understand before you use it, not least of which is that only 1 person can RD to a Windows XP machine and two (three actually, but that's another topic) to Windows Servers. Windows Servers can be turned into Terminal Servers at just the push of a button and the outlaying of cash for licensing, which will allow any number of people to connect to them.
To use this from the internet to connect to your network, you will need to port forward Port 3389 to the PC or Server that you want to RD to.
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