View Full Version : router/modem

08-26-2005, 07:03 AM
can you tell me difference of ADSL routers & modems?
which one is compatible with linux?

Harry Kuhman
08-26-2005, 07:39 AM
can you tell me difference of ADSL routers & modems?
which one is compatible with linux?

They are completely different devices.

The modem is the device that takes the signal from your cable (usually a RF connection with a center wire and a screw ring around it) and converts it into ethernet packets (do not accept one that connects to you computer by USB, insist on ethernet).

While you can connect that ethernet connection directly to an ethernet card in your computer, a router gives you a lot of advantages over doing this, these will be listed below. Occasionally a modem will include a router (particularly newer DSL modems, I don't know of any cable modems that do). But most users connect a seperate router to the ethernet connection on their cable or DSL modem and connect one or more computers to the router.

Routers used to cost $150 or more for a simple device. They have become extremely inexpensive, with some frequently selling in the US for $10 or less after rebate. This week both Best Buy and CompUSA have routers at $5 after rebate, and the CompUSA one even has wireless capability.

Features of a router:
Provide a true firewall hardware to protect your computer. Unexpected incoming attacks can not reach your computers.

Allow multiple computers to share the Internet connection at the same time. Most routers provide 4 wired ports that computers can be plugged into. This number can be increased by using additional "switches", these are devices very much like the router that automatically route or "switch" network traffic. Older "hubs" can also be used, although they usually are not as good a choice as using a "switch". Additional computers can also be connected on some routers by wireless access (see below). Most home routers can support, with the help of switches, at least 32 computers. Many can support as many as 254.

They provide the backbone of a Local Area Network, letting you share files between computers, or print from one computer to a printer on another, and similar local networking tasks.

Most routers have software features that let you control access features, but different routers have different feature sets so if you want to use these features it is advised to check the features of a model you intend to buy (most manuals are available on the manufacturer's websites). You can, for example, block some websites. On many routers you can control access for individual computers by time and day; so for example you can set the children's computers to not give them access after bed time on school nights. You can even have computers that can share the local network but not access the network at all.

Many (but not all) routers will conect to services like Dyndns.org to let you automatically track a dynamic IP address that your ISO gives you and let you use a permanent unchanging URL to access your home network (as long as the network's firewall rules are set to allow such access). This can allow you to run a home web server, FTP server or game server, for example.

The router takes care of all logging in to an ISP that require it and gives out local addresses on you network to users by DHCP. So you need no special connection software with Knoppix if you have a router, you just boot and you are automatically on the Internet when the boot is done, your network card set up automatically by DHCP.

Many routers support wifi wireless connections. These include 802.11b (11 Mb/sec wifi connections), 802.11g (54Mb/sec wireless connections) and the less popular 802.11a (also 11 Mb/sec on a different frequency band), as well as some more expensive ones that offer new wireless capabilities that have not been standardized yet.
I would not consider running a high speed connection without a router, it simply isn't safe.

Harry Kuhman
08-26-2005, 07:51 AM
Sorry, I was thinking you were talking about cable, but I just noticed you mentioned ADSL. All of the above still holds true, except that the modem does not have a coax wire coming into it, it plugs into a telephone jack and the output is still an etherenet connection.

Most DSL users need to run some sort of PPPoE or PPPoA software on their computer if they connect directly to the modem. If they use a router the router takes care of PPPoE/PPPoA and the users do not need to use any special software beyond the network software that is native in Windows and Linux.

Most DSL users do need to log into the Internet Service Provider with a User/password. The router takes care of this for you, once you have the router set up you don't have to log in manually at all. Knoppix just connects to the Internet automatically when booted with a router, you need to do a number of extra steps when usinf DSL but no router.

If you can determine what DSL modem you will be using you can check on the Internet to see if it includes a built-in router, some new models do but many do not.

And the advice to insist on a modem that supports ethernet and not accept a USB only modem, or a modem card that you have to install in your computer, still holds true.