A Tale of Two Cable Modems
I get a call from my Daughter. Her and her Hubby had just moved to a far west suburb of the urban area that I live in. They formerly had WOW! internet access via a cable modem. When they moved they went to Time Warner Roadrunner cable modem service.
Unfortionately when they set up their computer they could not get the monitor to display anything. My Daugter has email at her work so she was not too excited about this but her Husband only gets email access at home. After some calls back and forth I said I would bring out an old 15 inch monitor one of my Wife's friends had left with us while she was visiting several years ago.
Before I had a chance to go out and replace the monitor with the old one I had a 2nd Ammendment Rights group meeting that I attended. This is a once a month meeting in which local, state, and federal legislative moves are tracked and analyzed in regards to how they affect a persons ability to exercise their 2nd Ammendment rights.
I recalled from the last meeting that the group had several monitors they had received from a member who had gotten them from that members work. They were going to be thrown away but they were perfectly usable monitors. After this months meeting I saw a monitor setting next to the door to the back entrance right in line with a bag of trash and a medium sized plastic trash can. I asked if this monitor was to be thrown out and one of the officers said that no one seemed to have a use for it, being as most folks had gone to LCD monitors. I asked if I could have it and he was happy it found a new home. This was an older, (1998) NEC 17 inch monitor. That would be a far cry better than the 15 inch I had planned on taking out to my Daughter's place.
I took the monitor home and verified it was working well. Later on I managed to get over to my Daughters with the thought that this would be a short monitor replacement with no other worries. They also wanted a replacement mouse as their old Crystal Serial Trackball was on its last legs. I had several serial Microsoft mice so giving them one was not a problem. My Wife had come with me as she also thought this would be a fairly short visit.
So much for what we thought. The first thing I noticed when I got there was that my Daugther or Son-in-Law had plugged the monitor into the integrated VGA port on the their computers motherboard. Unfortionately for them this port was not the one they should have used. I had installed a PCI video card as the integrated video had a hard time playing the MPEG movies and other graphics that my Son-in-Law liked to watch. I moved their old monitors VGA connector to the correct card and Wa La, video was working.
Unfortionately the video working showed that the cable modem was not granting an IP address to the computer. This computer while older, had an integrated Davicom NIC,(network interface card). The cablemodem was an older motorola unit, a SB4100, IIRC,(if I recall correctly). I did not have any spare parts or computers for testing as I had only brought the replacement monitor that now appeared to be not needed. We got on the phone with Roadrunner technical support and they went through the normal things. Uninstall IP drivers, reinstall them, verify settings, request I test with other computers and so on. I was given to a tier 3 support person and he also tried resetting the modem numerous times.
I ended up giving up, as I did not even have a USB, (Universal Serial Bus), cable to try and hook the cablemodem up via USB instead of the NIC.
I decided I would come back with more things the next day in order to get this sorted out.
So, the next day I went out to my Daughters with two laptop computers, each having NICs, two 3C905 NICs, two USB cables, a CD I burned the 3C905 drivers onto, and two CAT5 cables.
My Daughter was a bit surprised when I showed up because I had gotten to her house early, before she left for work. I figured I could work on the problem while both of them were at work. I normally work nights and this was one of my days off, so my time was bit more flexible than theirs. I found out that She had sprained her back and was not planning on going into work unless it improved a bit.
The first thing I did was try a different NIC cable. This did not help. Then I installed a 3C905 card and installed the driver for it. Her computer has Windows 2000 Professional on it but it did not have the drivers for this particular NIC. After hooking everything up the problem was exactly the same. The computer's NIC saw the connection, as evidenced by it reporting when the cable was removed or intalled. Unfortionately I could see packets going to the cable modem, per the status information on the LAN connection, but no packets coming from the cable modem. As a last test I hooked up an old Thinkpad laptop I had to the cable modem so I could certify it was dead. The Laptop got an IP address from the cable modem! This was quite confusing. After trying both NICS and both LAN cables in my Daughters computer I decided that perhaps their was some kind of weird virus or other system problem keeping the computer from receiving data via its NIC.
I bundled the computer up and took it home with me. As it is much easier to work where you have other computers with Internet access working. Upon arriving back home I hooked the computer up. It immediately was granted an IP address by the router I use as part of my home network. Oh my, now I was truely confused. I put their computer back in the same configuration it had originally been in. Everything worked fine. Harumpp! What could be the cause of all this? I had a working cable modem as so far as it would talk to my laptop, (which I had left for my Son-in-Law to use while I had his computer), I had a working computer on my network that would not talk to the cablemodem at my Daughters and Son-in-Laws house. I had a working connection with that cable modem via an old laptop.
Logically, I thought, it had to be something causing this problem. After consideration I came up with the hypothesis that the monitor my Daughter and Son-in-Law had might be putting interference on the ground which was causing the cablemodem to fail in communications. With this is mind I and my Wife drove back out to my Daughter and Son-in-Laws house to test this theory.
Well, the theory once tested, was wrong. I hooked up the replacement monitor, the NEC 17 inch, and their computer behaved exactly as before. I decided to try and get the cablemodem connected to the computer via USB cable. I disconnected the CAT5 cable and hooked up the USB cable between the computer and modem. The computer did see the cablemodem and then of course asked for drivers. I did not have those drivers and I discovered after some searching that the Roadrunner tech had not left a CD or floppy with the drivers on them. I hooked the Thinkpad back up and was able to browse to Motorola's website and find they had drivers I could download. Unfortionately my Daughter and Son-in-Law did not have any floppy diskettes anywhere. I was thinking I would have to pop over to a store when I remembered that the Microsoft serial mouse I had hooked up had two driver diskettes. The first diskette was full while the second diskette had over 800K of space on it. I was able to copy the drivers over to that diskette and then use that to transfer them to the computer. After unzipping them I was able to install the drivers for the cablemodem. After this I saw that a LAN Connection number three had appeared in their network and dialup box. I did have to unplug the cablemodem to reset it before it started communicating via its USB port. Once it did start commuicating it established a 12 Mb link with the computer and this link worked fine as an internet connection. I had my Daughter test it out with her email account and I also did a bit of browsing to confirm all was well.
My conclusion from this was that this cable modem had some kind of weakness in its NIC port that caused it to have a marginal signal level on its transmit pair when set to 100Mb. I am guessing, as this was an older modem, that whoever had used it in the past had hooked it up via its USB port so its flakey NIC port was never discovered. The laptop's older 10Mb NIC card worked, and that means the 100Mb part of the NIC port on the modem was probably the culpret. I never tried setting the computer's NIC to 10Mb but my next hypothesis is that if I had it would probably had worked. The computers 100Mb NIC did work on my home system so I would rule that out as the problem, as well as the two 3C905 NICs failing in the same way.
This was one of my more perplexing problems which were made even more difficult due to the 40 minute drive to my Daughters and Son-in-Laws house. A less informed person would probably have faired better as they would have just had the cablemodem replaced and solved the problem. That actually had been my plan before the cable modem worked with the laptop. Sometimes having too much knowledge in an area leads to longer repair times as every option is tried and double tried before committing to a course of action.
My failure of logic was in not realizing the laptop's NIC could only do 10Mb and that it worked because of that limitation. It is much easier to analyze these kinds of situations after the fact than isolating it while in the trenches.
The one benefit from all this, aside from being made a little more humble about my abilities, is that an excellent Mexican restaurant was discovered about 10 miles away from my Daughter and Son-in-Laws house, on the opposite side from where I live. If anyone likes Mexican food be sure to try out the Los Mariachis in London Ohio on State Route 42 just north of London. It is on the west side of the road in a small strip mall. Their food is better than the best I had in Columbus Ohio.
