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Cable Modem woes



3:10 pm on May 31, 2001 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

I've been using a router on my cable modem for over a year. This morning I can't connect so I call the tech dept. Little techno weenie guy sees that I have 2 computers on behind my router! How can they do that? Then he tells me to plug in one computer at a time like I'm supposed to be doing and why do I have a router anyway.

About that time I heard the distant thunder of goosestep marching and a knock on the door....

What kind of new toy do they have now that could detect this kind of thing?


3:33 pm on May 31, 2001 (gmt 0)

10+ Year Member

Just out of curiosity - who is your cable company? Are you using NAT on your router? I'm assuming that they can see IP addresses, whether fixed or dynamic, although I thought NAT would block that from happening.


3:46 pm on May 31, 2001 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

Hmmm, that is strange. I had run a wireless network for my notebook from my PC for a year and a half. They said I had to pay for another IP#, but I just used Internet Connection Sharing (Win98SE) on my PC and it worked great. From what I understand if you use a router, they can't really tell how many machines you have. They do tend to run portscans, so maybe they found a hole?

You didn't mention you had a router, before he said anything about 2 'puters, right?

>why do I have a router anyway
Tell them because you want a hardware firewall. They are faster and don't require any PC resources.

Edited by: Drastic


3:46 pm on May 31, 2001 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

Time Warner.

I use a D Link 701 and I beleive it's running on NAT. Not my true area of expertise tho.

I can hook up one computer at a time just fine now.

I think in my recommendations to all the people I service from now on will be DSL.


4:21 pm on May 31, 2001 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

I just overwrote the old firmware files on the router and it works again. I had opened some ports for some video phone software (which never did work). I'll bet they found those open ports by scanning...how much you wanna bet?


8:13 pm on May 31, 2001 (gmt 0)

Same provider here. I run a proxy PC with Sygate that uses a second nick to go to the hub.

Deathmatches aplenty now for three years ;).



11:37 am on Jun 9, 2001 (gmt 0)

WebmasterWorld Senior Member 10+ Year Member

I used to be a cable tech, I bet they did not know you had two computers, what I bet they knew was that you had two different mac addresses.

On DOCSIS modems, they register the MAC addresses of any device that hooks up to the cable modem, even if it is no longer hooked up - even if the cable modem is unplugged - it stays in memory and the Cable company can see it anytime they Poll.

If at one time, you had the computer hooked up directly to the cable modem, that is one address they recorded.

If you then added the router, they recorded that one as well. I do not believe they would detect a computer behind the router itself. I know the modem itself can not.

99.9% of the people on the phone do not understand most of the stuff on the screen. I have talked to 100s of them, and most do not know what they are doing.

I have seen the internal software cable modem providers user to track their system. While they do track your MAC address, amount of data transfered, DB level of your line, packets resent, and other stuff - they make no effort to determine the number of computers. I do not even believe there is any option for that.

On many cable modems you can access the internal DOCSIS screen by going to in the browser itself.

You will see the list of MAC addresses I am talking about.

The people on the phone always jump to conclusions. By the way, I have seen many routers fixed just by doing a flash upgrade. This has happened on three of the Linksys routers I have used or helped install.

The Linksys router will also let you spoof MAC addresses in case the bozos at the cable company have a problem with your MAC address.

Then again, this was for only one company, other companies may vary. The DOCSIS standard is pretty strict though, and I do not recall seeing anything in there for individual computer monitoring off one IP - I could be wrong though - it has been a while since I read it.


5:43 pm on Jun 12, 2001 (gmt 0)

WebmasterWorld Administrator brett_tabke is a WebmasterWorld Top Contributor of All Time 10+ Year Member Top Contributors Of The Month

So rr or @home don't allow you to run more than one machine per ip address? Is that in thier tos? What are people doing that have a whole house full of boxes (mom, pop, sally, jr) ?


11:56 am on Jun 13, 2001 (gmt 0)

Hi Brett,

I am on RR. I have the cable modem feed to an old P90 that has two network cards and runs a proxy server package (You could replace this with a cable modem router. Linksys makes a nice one). The second network card feeds to a 24 port hub. I then have a N*vell 5 server and 4 print servers that hang out with two games PCs, one work PC, a kids on-line home school PC and a laptop in the family room.

I am a LAN Admin for a N*vell shop and spend 40% of my time doing Intranet work, when I get off after a long day and drag my behind home I get hit with....

You guessed it, the same thing. Work on my e-comm site and adminstrate the LAN and do break fix plus throw in the normal house work to boot. Oh yeah, your favorite topic, deal with sales calls (Grrrrr).

I tell people I have a passion for these things, I'm starting to wonder if I am just plain crazy ;).



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