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Internet
Sharing
Introduction
You can share a cable or DSL Internet connection among multiple
computers. The same principles also apply to ISDN lines and, in
some cases, dial-up lines.
Microsoft provides Internet sharing with Windows 98 and later versions.
This sharing works reasonably well and it is fairly simple to set
up, however, its simplicity can lead to operational and security
concerns. The information in this tutorial does not cover Microsoft
Internet sharing.
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This information is provided for your convenience. We make
no claims for its accuracy, its reliability, or its completeness.
There are numerous ways to set up a network and we cannot
guarantee that these instructions will work for you.
Please use your discretion and common sense when making any
type of buying decision and when dealing with computer professionals,
retailers, and service providers.
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Your Internet Service Provider, or ISP, probably does not support
a shared connection. Therefore, you will need to set up Internet
sharing in stages. This article is organized with the assumption
that your Internet connection is installed and possibly functional,
however, you can jump around as needed after you have read through
the material.
- Get your Internet connection working one one computer.
- Build a network and ensure that at least two computers can talk
to each other.
- Set up your computers to share one Internet connection.
- Add additional PCs to your network.
- Set up a firewall to protect your PCs from the Internet.
- Ensure you can restore the connection to a single PC without
a firewall if you have problems with your service. Most ISPs will
not troubleshoot a shared connection or one that has a firewall.
How Internet sharing works
Every device accessing the Internet is identified by a unique IP
Address. Your ISP normally provides one you with one IP address
and it is subject to change at any time.
Each of your computers must also have a unique IP address. For
Internet sharing, a Gateway is used to bridge all of your
computers to the Internet. Through a process called Network Address
Translation (NAT) each computer appears to have the same Internet
IP address.
NAT adds a header to each outgoing message to identify the
originating computer. This allows replies to be rerouted to the
correct computer. NAT is rather complex but fortunately that is
invisible to the end user.
Internet Security
Cable and DSL connections are "always on" and therefore
each computer on your network is vulnerable to attack. You
should have a Firewall plus virus chacking software to protect against
viruses and other attacks. Hardware gateways generally include a
firewall. Software gateways need a separate firewall. You can read
more about security in the Resources page.
Connecting to your office network
If you want to connect with your company's Virtual Private Network
(VPN) you should consult with your company's network specialists
before putting any Internet sharing solution into place. Your solution
must be compatible with their VPN.
- If you have a software firewall on your computer you may not
be able to connect to a VPN. There can be conflicts between
these two forms of security.
- Some companies require connecting to their VPN with a laptop
or a desktop PC that they support. This system may not be
able to see the rest of your network.
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