networking an Internet connection with a router
If you want to network your Internet connection, that is share it with several computers in an office, there are several things you should be aware of.
You can use Microsoft Internet Connection Sharing to network your dial-up ISDN connection over a LAN, but it has limitations in terms of security and firewall configuration. In addition, the host machine has to be up and running before any others can connect.
A more robust method of connecting a network to the Internet is via a router. The router becomes the gateway to the Internet for the network, and should be able to filter unwanted or insecure data packets in both directions, acting as a firewall. Modern routers can automatically allocate sub-addresses to machines on the LAN and use the single dynamically allocated IP address issued by most ISPs for network connection - or static IP addresses supplied by your ISP can be configured on each machine.
Some routers need to be configured (at least initially) using a direct cable connection to a special port and typing in command lines, but increasingly they install themselves automatically on the network and can be set up through a graphical user interface using a browser.
The LAN is normally via ethernet ports, but the WAN or Internet side can be by modem, ISDN, ADSL, cable or ethernet - so it is important to choose the right model for your method of connection.
If you are using a metered dial-up connection it is important to realise that lines can be automatically opened by network traffic. An ISDN line makes connections unobtrusively - no dial tones or modem chatter - which can result in enormous telephone bills for the unwary. The router must be configured to filter out unwanted traffic (normally a default filter is provided), and the "auto update" type applications, which can check on the Internet for updates every 5 or 10 minutes, running on each PC, such as automatic Windows upgrades, must be stopped from loading at start-up.
The router can be configured to drop the line after so many minutes of activity - with an unmetered connection this doesn't have the same cost implications, but it could tie up lines unnecessarily.
You may need to use a program to identify spurious network traffic, called a packet sniffer - try a search on Tucows.
Reviewed January 2011
last updated : 21/01/2011
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