Getting in the Fast Lane

Here's how to set up a broadband connection for your home or office LAN.

With the arrival of technologies such as cable modems and xDSL (digital subscriber line) technologies, individuals can now have a moderate to extremely fast constant connection to the Internet, instead of the usual analog telephone-line-based modem. Such new technologies use different hardware and sometimes, as in the case of cable, a different transmission medium.

In this article, I will describe how to set up a cable modem with a local area network (LAN) to provide a fast connection to the outside world. However, you don't need to have a cable modem to benefit from this article, just a fast and constant/semi-constant connection to the Internet, such as ISDN or Frame Relay. The setup procedures are almost the same, with the exception that your hardware may require special drivers. Contact the manufacturer for details on support.

Cable Modems

There are three types of cable modems on the market today. One is the static type, which is always up and connected. This type is generally expensive and has a static IP address. It also offers two-way communications for downloading and uploading as well. This is the best type of modem to run a web, FTP or TELNET server. The second type of modem is the dynamic cable modem, which also offers two-way communications, but has a login procedure, where you are assigned a dynamic IP address each time you wish to use it. Such modems use a DHCP client to obtain a dynamic IP address from the headend server. The third and cheapest type of modem on the market requires that you use a telephone line to upload information, such as web page requests, and use the cable to download information, such as web pages. This type of service is generally inexpensive, but suffers from extremely high latency. This isn't the type of modem to set up a server on, since the upstream connection is so slow. However, this type has blazingly fast download speeds.

This article will focus on the first type of modem, since those are the most common. There are excellent resources on-line for all types of modems. An excellent page for the dynamic modem is This page has links to software needed such as DHCP clients and a login program for RoadRunner modem customers. A good resource on how to correctly set up DHCP for a cable modem can be found at The third type of modem, a cable modem that uses a telephone line to upload data, is pretty much controlled with proprietary software and hardware. These solutions are in place because of the high cost of outfitting existing cable plants for two-way communications, which is a basic part of the cable modem theory. Such solutions require hackish, kludgey software solutions on the Linux side. A blend of DHCP and PPP must be used to get the routing to work correctly, but after it's done, it is ultra fast. Consult the PPP HOWTO for help in getting your analog modem correctly configured. For the cable modem part, follow the instructions shown here or on the aforementioned web pages. The DHCP should work in the same manner.

With coaxial-cable-based Internet access there is no signal degradation for many miles. At this time, cable is the favored high-speed, low-cost connect method for homes and small to medium-sized businesses due to reliability factors. Cable Internet access availability is spreading to more areas each day.

Cable modem packages generally include a modem lease or purchase fee along with a service fee. Leases usually cost between 15 and 20 dollars, and service can cost from 35 to 70 dollars a month, depending on location. Speed varies from service to service. For example, @Home and RoadRunner offer speeds that are extremely fast—equal to multiple T1 performance in uploading and downloading. However, services such as GTE charge twice as much and have speeds that compete only with double ISDN, which operates at a transmission speed of 128 kilobits per second, which is roughly 15 to 16 kilobytes per second. It all depends on your provider.

xDSL Technology

xDSL Technology uses the same copper wires that have been in place for decades with hardware on both ends to accelerate data transfer. One drawback to this method is repeaters and/or amplifiers must be used along the route to prevent signal degradation. xDSL as yet remains untested and extremely expensive in terms of service and hardware. In fact, xDSL technology is still considered to be in the testing phases at this time (February), so I will focus on cable technology in this article.

xDSL technology, the telephone company's answer to cable modem technology, will probably be more expensive. There isn't an average price, since the whole technology is in its early stages. You can expect to pay anywhere from cable modem prices to several hundred dollars a month to get this service. However, the speeds of the service are phenomenal for the transmission medium. The speed you get depends on your telephone company and location.

With these two new technologies, how is the Linux user supposed to exploit them to their full potential? Easy. With a few simple pieces of software, you can have a full in-house network with a simple firewall, capable of World Wide Web browsing, Internet relay chatting and connecting to the outside world via FTP from each of the computers. Software such as CU-SeeMe, a video conferencing program, have IP Masquerading modules in order to work in this environment. Note that IP Masquerading does not allow for incoming connections to the client machines, so the client machines are truly client machines.