To communicate with different networks (that is,
computers with IP addresses that use a different network portion), a gateway
must be used. At its simplest, a gateway is any device which has two or
more network adaptors, each connected to a separate network. Computers on
one network can pass data to the gateway, which then forwards it to the desired
computer on the other network. This is the fundamental structure of the
The default gateway address shown in by the IPCONFIG command you tried just a moment ago indicates where
data will be sent if you try to contact an IP address outside the local
network. In the case of most home network setups, the default gateway
will be the router or Internet sharing device.
Public and Private IP Addresses
As far as this Beginners Guide is concerned,
there are two types of IP addresses; private and public. Private
addresses are usable only within private networks and cannot be used on the Internet, as
the gateways that make up the Internet will refuse to pass on
information coming from a private IP address. Public addresses are Internet-ready,
and can transfer information to any other public IP address over the
Internet. When a PC connects to an Internet service Provider, it receives a public IP address (or the
home router used to connect one's network does).
If you have a home network using a router or Internet-sharing device, each of
the computers will receive a private IP address from the router, which in turn
has received a public IP address from the service provider. When one of
the computers uses a browser to connect to the Internet, the router receives
the request first and replaces that computer's private IP address with its
public one. When the web site data comes back from the Internet, the
router performs the same operation in reverse, sending the data to the computer
that requested it.
Dynamic and Static IP Addresses
Depending on the Internet service provider, a PCs public IP address is either static or
dynamic. Static IP addresses are usually found in 'always on' services like
cable Internet connections and never or rarely change. Dynamic IP
addresses are common to DSL Internet providers and change every single time the user
connects to the service. No additional steps need to be taken to host a
website on a static IP address connection, but hosting on a dynamic IP introduces some
complexities which PCSTATS will cover a little later in this Beginners Guide.
DNS: The Friendly Face of the
Before we show you how to install Apache web server and start hosting a web site, you'll probably want
to acquire a DNS domain name for that website. This will allow visitors
to type 'www.(yoursitename).(com\org\ca\whatever)' to visit the website instead
of having to memorize a server's 9-digit IP address.
DNS (the Domain Naming System) provides a simple way
of navigating the Internet. Instead of having to memorize the IP address of
each website, users can simply type a friendly URL like www.pcstats.com to get there. The DNS
name (www.pcstats.com) is mapped to
the IP address of the PCSTATS web server, allowing anyone to visit
our site without knowing its current IP address.
A system of DNS servers shadows the growth
of the Internet and provides a means of connecting DNS names with web
servers. When a person acquires a domain name through a registrar site, the IP address
is linked to that name, allowing users to connect to a web server via the
URL system. A central governing body (ICAAN) controls the allocation of
domain names, ensuring that the system remains conflict-free.
When a user types www.pcstats.com into
the browser's address bar, the computer sends that address to a DNS server on
their network or the Internet, looking to have it translated into an IP address
that it can contact directly. That DNS server will send back the IP address if
it knows it, and if it doesn't, it will contact other DNS servers all the way up
to the root of the Internet until it finds the address it's looking for. The
entire process generally takes less than a second.