Need advice on connecting a router to a cable modem.

WARNING: I have no idea what I’m talking about.

A friend needs advice on connecting a computer to the modem of another computer.
What type of hardware is needed, and what changes need to be made to the software?

TIA

Hang on. The text of your message doesn’t match the subject. Is the person trying to hook two computers up to a cable modem? Are they trying to share a 56K modem connection? Where does a router come into the picture?

I think she’s asking about networking.

Maybe.

Yep, networking. I don’t know what a router is, but that’s what my friend told me to ask about.

Oh, and he would rather not use a hub.

Need lots more info to give you a cogent answer but I’m going to take a sophisticated wild ass guess that this is what your friend is talking about.

Linksys BEFSR41

This is a popular router + hub/switch + firewall that will let him plug in his cable modem to the WAN port on the back and let other computers (up to 4) plug into the other ethernet ports on the back of the Linksys box and share the cable modem’s net access and network with each other. They run 70 - 90 or so.

The “trick” to this though (at least for my old DSL connection) is that you need to set up the router itself to log onto the internet. You can telnet or use a web browser to access the router and set up your username and password and whatever else you need to do, so it’s the router that’s “connected” to the internet, even if there are no computers plugged into the router.

You need a cable.

Either a crossover or a nomal cable, but your friend needs to consult the fine manual.

During the school year I run three PCs that are all connected to an AT&T cable modem via a Linksys 4-port router. Set up was reasonably decent after the AT&T guys came out to install the cable modem unit. Upon making all the necessary connections, it is a simple matter of designating one of the three computers as the admin and using that computer to dial into the router’s onboard setup utility which allows the user to specify how many computers there are in the LAN and so forth. The setup utility was reasonable straight-forward and well documented (at least with my router). I would like to point out that, prior to using a cable modem, we attempted to network the apartment using DSL and that ended up being a nightmare as Qwest had some horrific protocols in place that made it nearly impossible. Also, it is important to note that if your friend is intent on using a hub rather than a router, it will be quite complicated to create an actual working LAN-- that is to say that the threee PCs in my apartment don’t “know” about eachother. If file sharing is important to this individual, he should consider a hub.

So you want to share one cable modem connection to two computers, right?

There’s a couple ways. One way is to put a network card in both computers and then share the cable modem with a hub device. This is cheap as hubs are dirt cheap these days.

Internet -> cable modem -> hub ->both PC (two cables, one to each PC from the hub.)

For this arrangement, your Cable ISP must allow you to connect multiple computers because each computer must get a separate address from the ISP. AT&T Broadband charges $5 for each computer past one. Note, though, that any shared things between these two computers are also inherently shared to the internet. Careful configuration can minimize the danger but I don’t like the exposure.

The firewall/router like the Linksys BEFSR41 mentioned above looks like the above “picture” but replace the “hub” with the Linksys. This arrangement is nice because the multiple computers are hidden behind the Linksys.

The Linksys will provide “NAT”, Network Address Translation, toward the internet, dividing your home network space from the internet space. The IP provided by the Cable ISP is assigned to the Linksys, the Linksys provides a different range of addresses to each computer connected to it. The Cable ISP has no idea how many computers you have so you only pay for one connection and the Firewall capabilities of the device make sharing resources between the two PC’s much safer. This is my preferred method. The Linksys manual provides good information on the nuts-and-bolts of configuration.

Yet another method is using the Win98SE "Internet connection sharing which looks like this:

Internet ->cable modem -> PC1 -> PC2.

In this case, the PC1 is providing NAT service for PC2. This creates a dependency that PC1 has to be up for PC2 to get to the internet. It also makes the same sharing-to-the-internet vulnerabilites that make me nervous about the first example above. I’m unsure if Microsoft allows sharing to an ethernet connection or if you’re limited to sharing a dialup.

All things considered, I’d recommend the Linksys.

Geek warning: some of the above is a simplification but this was worded for the novice.

Okay, I have a question regarding the Linksys router mentioned in a few posts.

I have this router, and I bought it partially for the firewall protection it says it provides. And Belrix noted that it should hide the two computers hooked up to it. But my cable provider, Comcast, has said that they know we have two computers hooked up to it, even though we’ve never told them.

Q1: How do they know?
Q2: Is there anything I need to do to setup the firewall, or does it work automatically? Will adding firewall software (Norton or somesuch) help? (Both computers are Macs)

All you wanted to know about NAT

A1: Basically, multiple addresses on the private side of the firewall are translated to a single address on the public side each with a different port number. If the host ISP is sniffing packet contents, which they can do, they can see the differing ports and deduce that you have multiple nodes on your private side.

A2: Most firewalls come out of the box with pretty good default setups for protection of your devices. These settings can be loosened or tightened further with additional configuration. Be sure to upgrade the firmware in the firewall after initial installation.

SanibelMan, AFAIK, they shouldn’t. My DSL ISP had no idea (though they asked) when I had to call 'em for tech support of some sort or another.

Every network card has its own MAC address, which may be part of how they know, though I don’t believe this info is ever sent out with packet requests or the like.

Thanks everybody. The responses have been very helpful.