Hub/Router setup question for RoadRunner in upstate New York

You need to turn off the DHCP and routing function of the Router (or get a simple hub) so that the ISP's DHCP assigns IP numbers to each of the PCs. Then and only then will each PC get it's "full" bandwidth.

(Not that you will no longer have a LAN, but 3 PCs on a WAN. You will have to teach each PC the IP address of the others, and all your local trafic will be 'exposed' to the internet.)

- RM

Of course they can triple the fixed amount you get so, in essence, you would have triple the bandwidth of everyone else (unless they also have

I believe bandwidth is limited by the cable modem's config file, not by the number of IP addresses you're allowed to pull.

The DOCSIS method of capping bandwidth is by capping the modem. Theoretically you could achieve a per-IP cap at a router past the CMTS. So if the business account IP were to be capped at, say, 5000, and each of the two other IP's were capped at 3000, then the DOCSIS modem would need to be capped at 11000 or above, or not be capped.

This would be a very odd-ball set-up, and I don't know of any large cable providers currently doing it that way. Typically the providers take advantage of just the DOCSIS method of capping the modem.

So to recap on caps (pun intended), the scheme you describe is not a function of the DOCSIS system, but could, in theory, be something added on outside the DOCSIS system.

Most Docsis compliant cable modems have the ability to handle three IP addresses and throttle per each. e.g. this lets there be 2 home and 1 business account on one modem.

What brand modem and model do you have?

No. Your cable modem gets a fixed amount of bandwidth. If you have multiple IPs, they share the available bandwidth on a demand basis. That is, if only one device is trying to use bandwidth, it can use all of it, but if two devices are trying to use bandwidth, each gets half. Class of service is intended to prioritize bandwidth so, for example, your VOIP packets could take precedence over FTP packets, but most cable systems don't support it yet.

-Larry Jones

I don't think math is a science, I think it's a religion. -- Calvin

I've never heard of an MSO that does that. Not even the ones that charge extra for additional IPs.

-Larry Jones

We don't ATTEND parties, we just CRASH 'em. -- Calvin

It doesn't matter, all DOCSIS modems work that way. The bandwidth cap is on the modem, not the IP address.

-Larry Jones

How am I supposed to learn surgery if I can't dissect anything? -- Calvin

You heard wrong.

And how do you expect someone to cite a source for something that doesn't exist when you're not willing to post a source for something that you think does exist? It's up to you to show he's wrong in saying it doesn't work that way by showing an example of it working that way. He can show 1,000,000 citations showing it working the way he says it's done, but that doesn't show he's right, and you're wrong. All it takes is for you to post one concrete example showing it works the way you think you've heard.

BTW... While each MAC gets it's own IP, and each IP can be assigned to only one MAC, it does not follow that each IP must be a separate NIC because a NIC can have more than one MAC. (A NIC can have more than one interface, and each interface in use must have it's own MAC.)

Do you have a source for that? I have heard (but I too am sourceless) that "some modems" have the ability to recognize up to three MAC addresses and throttle each. This is possible because the modem uses a version of time division modulation for upstream transmissions. In other words (what I have heard is that) each IP gets a separate time slot. [Note that each IP must be a separate NIC (by definition).] - RM

That's a play on words IMO. You can have an adapter card that has more than 1 ethernet interface (but it's highly rare in the PC world). People tend to think of a NIC as being a single interface. So although the stmt is correct - it's far from the norm. It's pretty much the same thing as combining 2 or 4 (for example) NICs into a single card - everything is still pretty much treated as separate devices and you could logically think of it as 2 or 4 NICs rather than 1 NIC with 2 or 4 interfaces. I played with cards like this years ago on Sun workstations.

Maybe. But down boy !!

Never heard of that!

You're right. Multiple physical interfaces on NIC's are pretty rare for PC's. But it also slipped my mind that multihoming is fairly common. In that case, the same physical interface can have more than one IP address, so a MAC can have multiple IP's, and thus a NIC can have multiple IP's. This is actually fairly easy to setup on Windows NT/2000/XP, though you'd probably see it implemented on servers rather than workstations.

I'm playing with cards like this on Sun servers TODAY. :-)

Interesting - I haven't been on a Sun much since '96, so that's almost a decade ago. Those boards were like $1000 or so back then (maybe another $1000 or so for a 1GB ext disk drive [with fed discount]) - wonder what they go for now. ;)

I'm using servers with the Sun GigaSwift UTP 10/100/1000 PCI-64, Sun P/N X4444a, which has four RJ-45 ports and a list price of $895*. It's the upgraded replacement for the old Quad Fast Ethernet (QFE) cards from a few years ago.

The DOCSIS specs are online at .

It's possible that some modem manufacturer would implement such a non-standard enhancement, but it's not very likely. Implementing standard class-of-service priority between different addresses would probably be much more useful.

-Larry Jones

Who, ME? Who?! Me?? WHO... Me?! Who, me??? -- Calvin