Home Networking with a One Way Cable Modem?

Blacklotuz asks: "I recently networked the computers in my house with a Linksys EtherFast Cable/DSL Router. Today I called up Comcast to order cable internet service, but because I live in a rural area we still have downstream only cable. I was told that in order to use the service I would have to connect the cable modem to the ethernet card on my computer as well as dialing up via the 56k modem. Im running Windows XP on the computer that will be dialing up. Does anyone know of a way to use a one way cable connection with a router?"

Comments

with a router?

[tenman]

Why would you need a router? If you only have one machine, then you are set to go without a router.

If you have two machines, then you have two options as I see it. First (1) is to use the XP box to proxy the I-Net connection out to your other box, or (2) set a third computer up to do that for you. Any machine that has a routing table like the one that they are asking you to setup will be robust enough to handle any day-to-day routing that you might be talking about.

If that doesn't answer you question then, I guess you want a black box router that you can run through. All I can say is "My condolences to your dreams". After a cursory look over the web I have found plenty of routers with Ethernet/serial ports, but the thing is they use them as separate ports, and you want to use them as a MUX of sorts. If you got a cisco2500 (?) then you might be able to route all outbound traffic to one side of the box, and allow inbound traffic to run in from anywhere.

I'm not so sure that this would allow you to make and maintain a connection to your dialup ISP, but it may make your dreams come true. Also note that compared to my earlier solution, this one would be VERY VERY expensive.

This isn't that hard

[PD]

Plug the Linksys into the cable modem. Plug the computer into the Linksys. Plug the phone line into your computer. The Linksys should be transparent to you. It should be opaque to the rest of the world.

More Info

[bassburner]

I have the same situation setup right now through RCN. I likewise live in a back-asswards area with only one-way service. The cable modem connects directly to the modem through a standard modem cable. The cable modem than plugs into the Linksys router which plugs into the hub.

use linux bonding to solve this?

[fist_187]

you might be able to use a linux server to do this. i'm not sure if it would work, but here's the idea:

1. you'd need a linux machine, phone modem, and 2 ethernet cards (one for the cable modem, one for the router).
2. use the linux bonding driver (multilink) to combine the phone modem interface and cable modem (ethernet) interface.
3. set up ipchains or netfilter to make all traffic go through the bonded interface to the router interface and vice versa, preventing any from reaching the linux machine itself (you want the linux machine to be transparent).
   
   that should give you the single bi-directional interface to plug into your router. you might also try
   
   
4. running it as a halted firewall for a bit of added security.

i don't know enough about bonding to say whether this would work or not, can anyone help me out here?

what about the simple route?

[carpediem55]

Why not simply set up one of your machines as the router. Hook the internet into it. THen hook that into your network, since I assume right now your only using the switch part of the linksys box anyway. THis will turn the main machine into a router. If you want to be able to dial out from any machine in the network, you could use something like VNC or pcanywhere. You can then sell the linksys box and just get a switch, using the money for other things. Windows XP makes all of the networking INSANLY easy. Just run Network Setup Wizard.

Re:more information

[fist_187]

a cable modem is a bridge, not a router. unless it has 4 ethernet ports and says "router" on it, a cable modem bridges DOCSIS protocol to ethernet protocol.

a router doing IP masqerading (the linksys in this case) needs to know the outgoing data so it can correctly route the incoming data. so, you can't hook the router up between the computer and the modem and expect it to work.

Not possible

[EdMcMan]

It is not possible to have a linksys router do NAT on a downstream only connection. Why? - The way NAT works is (partially) by identifying outgoing sockets. Without this, NAT is useless. On the other hand, you could use proxies however.

To use NAT though, both the upstream and the downstream must be connected to the same routing device. An old computer would do the job nicely.