I thought I understood the difference, but it's not quite clear. The Cisco 678 is labeled a router, but the best I can tell is that it's an external DSL modem. I have an internal DSL modem and want to add an external to another computer. I know the 678 will work, but will other 'routers' also perform the same modem funtions, while simultaneously allowing me to network? If they called it an external modem, all would make sense. What am I missing here? Thanks.

I'll give you the nickel tour.

Modems, in today's venacular are designed to support a connection for one device (computer) and one device(computer) only. Routers, because of their greater intelligence, are designed to support more than one device (computer).

I never heard of anyone having an "internal" ADSL modem before, but not to say it doesn't exsist, I just haven't heard of it. The reason why is ADSL needs a modem that acts as a "spliter", that is the ability to spilt an analog phone call from a digital "data" signal. That is what allows people with DSL to use their phone and the internet at the same time. Phones only take up a fraction of the bandwidth over copper phone wire (about 4 khz) which means there is plenty of room, almost 90%, of bandwidth left over to transmit data. All you need is a DSL modem to know how to divide out the analog from the data and Voila ADSL.

Routers are intelligent devices able to work not only with several devices on "A" network, but several devices on "different" networks. That is to say if all your equipment is using the IP address on the network of 192.x.x.x, and your ISP is using IP address of say 65.x.x.x. Your router is able to "route" information between 192 and 65. A modem cannot do that.

A modem will dial into, in the above example, of network 65.x.x.x and give the connected device a network id of 65.x.x.y to put your computer on that network.

That means that the router is intelligent enough to connect multiple devices (computers) to a network, but a modem is not.

Other "routers" will perform the same funtion! That is their creation by design.

Modems will not.

Please feel free to elaborate on your question if additional clarification is needed.

D

It's not really a question of router vs. modem, but how a router and modem work together to share your internet connection.

Some (very few) people have an internal ADSL modem in the form of a PCI card. This is extremely limiting as the only way to share the connection is via an internal Ethernet card.

If you were given an external DSL modem, you have the choice of plugging the modem into your Ethernet card and sharing the connection through a 2nd internal Ethernet card (harder to configure), OR plug the external modem into a router and have the router (usually with mulitple built-in ports) share the connection. In this case, the modem facilitates the DSL connection and the router implements NAT (Network Address Translation) to share the 1 IP address among all your PC's. Many people are provided the modem by the ISP and go out and buy a home-use router such as "Linksys" products.

To answer your question, the Cisco 678 has a WIC (WAN Interface Card) slot that accepts a ADSL WIC. The ADSL WIC is the modem. So in your case the modem and router are combined into one machine, which might lead some to believe that it is an external modem. But it really is a 2-in-1 product. The phone line comes directly from the wall jack into the router. I believe the Cisco 678 has only one port on the LAN side, so you will need to plug a hub or switch (via a cat5 ethernet cable) into the LAN port and share the connection from there. If you do not need to share the connection among other computers, be sure to use a 'crossover' cable to plug the PC directly to the router.

Does that help?

D & Kalortpor,

Thanks for the inputs. I probably wasn't quite as dumb as I sounded, so most of the information I was asking was answered in the Kal's post about the 2 in 1 feature of the 678. I wish I had known more about the limitations before I picked the internal modem as the 678 was also an option. I figured one less piece of equipment on my desk would be a good thing, but not in this case.

I guess now I just need to figure out which other routers besides the 678 also have the 2 in 1 feature. By your description, I would say that there aren't many, but I don't know. That doesn't seem to be a common piece of information in advertisements for routers. Thanks again for your help fellows. It's guys like you that make computing.net the best tech support out there.

By the way D, it's an Intel Pro/DSL 2200, except for the little routing problem. I have an ethernet card in my system, but this whole problem orignated when trying to get my XBox online. Right now, no configuration works with an internal modem and ethernet card. I need to have external modem/router or hub setup. Anyway, thanks again for all your help.