why does my comcast modem keep resetting

We have static ip addresses and the modem is in the bridged mode. 1. Computer A with a web server and a dns server running Windows 10 pro. 2. Computer B with a web server, dns secondary server, and an email server running Windows 10 pro. 3. A netgear wireless router providing wireless to customers
Last week we moved from DSL to Comcast cable. Since the cable was installed we have an issue where the modem will reboot randomly. Sometimes two or three times an hour, other times it may go several hours before rebooting. We never had this issue with the DSL and the computers we had with DSL have not changed. Comcast has changed the modem (Cisco DPC3941B) and tested the line thoroughly. Our upstream and downstream levels are perfect and they have not fluxuated for the entire time. Our building has several other comcast customers and they have monitored them and us at the same time and none of them go down when ours reboots. After ruling out the cable and modem as an issue, the next thing we did is look at our machines. We removed the netgear wireless router but the reboot still occured. Next, leaving the wireless router off, we removed Computer A, and soon the reboot again occured. Next, leaving both the wireless router and Comptuer A off the network, we removed Computer B and waited. After 2 hours there was no reboot. Based on this we conclued that Computer B is having an issue with the modem. On Machine B is we shut down the Web server, DNS server, and Mail server the reboots seem to stop (we give 5 hours for a test as this is the longest we have gone without reboot since the beginning) We then try turning on the mail server, and soon a reboot. We disable the mail server and turn on the DNS server and soon a reboot. We disable the DNS server and turn on the email server and soon a reboot. No matter which server runs (alone) the reboots begin again. We have scanned the machine for virus, malware and rootkit (as we do very often) and it is clean.


We have disconnected the ethernet and connected via wireless to the modem with the same result, so a faulty nic card has been ruled out. Comcast has sent techs out 6 times in the 8 days we have had their service and they cannot find the problem. One tech suggested "maybe it is an attack", so we set the network monitor on and waited for an attack and the network usage was unchanged immediately before a reboot. Also it seems unlikely that an attack would reboot the modem, the modem logs only show the modem getting its address after it powers up again. No other info is in the modem logs. Can anyone suggest ideas on how to isolate this problem? Again the same equipment functioned over DSL without any issues for years. Although comcast seems to be doing all they can (tech sat in my office for several hours Saturday morning as we monitored and tried different things unsecussfully), we obviously cannot functions with random 5 minute drops throughout the day. We process our credit cards through Computer B and when it goes down we are out of business until it comes back up. Hello, I ve been having this issue with my modem resetting randomly several times a day for almost 4 months now. I ve kinda have been in the just deal with it phase with this technical issue since Comcast doesn t seem to understand what is wrong. I ll try and be brief with the situation as I can always provide more detail if anyone needs it. First off, my technical experience with computers is pretty high as I ve been working and building them for the better part of 10 years. I know what a modem does, what a router does and how they interface and talk with the computer. I also know how to do basic and more advanced troubleshooting with that kind of equipment should it not be acting right. When the problem first started, what was happening was that all the lights on the modem would shut off except the power light and then all of them would slowly start blinking again as it came back online.


Given that we ve had Comcast for some time at this point and we were still renting the modem they give you, I had determined that either the problem was on Comcast s end or that our modem was going bad. My testing of this theory came from hooking the modem directly to the desktop next to it to bypass the router and any issues it may have brought to the table and did this for the day. The problem still happened in normal frequency and I tried multiple Ethernet cords and several hard-reboots of the modem (unhooking the coax too) with no luck. I decided to buy a docsis 3. 0 modem model which is compatible with Comcast s service as it says so right on the box. I go home, call Comcast to give them the serial number and MAC address of the new modem and it comes online just fine. The next day, the same problem started happening again at the same rate every day. This goes on for another few days before I decide to call Comcast for some help since I keep hitting dead ends. I explain my situation to their tech support, who have me unhook everything and then hook it all back up, power cycling everything. The internet comes back up and tech support believes they ve accomplished their goal but I tell them that power cycling isn t what was needed because the modem just restarts itself several times a day and that I ve done the power cycling thing several times already. I told them I even left the modem with just power and the coax cable and nothing else connected to it for 2 hours and it still happened 3 times during that short period of time. They send a tech out who my roomate let in while I was at work. I come home and find out the guy tested the coax panel on the wall and said the readings were fine (I assume this meant testing the electrical output readings are in normal range and not surging or sagging). I also came home to a new modem, courtesy of our technician. My roomate said that the tech told him that it s most likely the modem causing the issue since he can t see any other reason and unhooked my brand new modem and hooked up one of their models I ve never seen before.


Of course, because he power cycled the whole deal, it was working when they left but the problem still persisted, for at least another week before I broke down and called Comcast again. Another tech comes out to our house but I was home this time. I explain the situation to him and he gets to work and eventually replaces the line coming from the phone lines in back to our house. He said it was pretty badly weathered and that it looks like animals may have been gnawing on it, exposing the wire. We put my modem back on and have him take the one they provided back and to remove the $8 renting charge from our bill. SUCCESS, the internet stays on consistently with no reboots for about a week and a half before it starts doing it again. It s been doing this again now for over a month and I m just not sure what else to do. Tech support just has me power cycle everything and then if they can t figure it out from there, they re lost on what else to do. 3 modems, 2 technician visits; still the same problem persists. What should I do? Obviously most of us struggle with the legal monopolies that are our ISP s in this country but this is just unfair. I pay the full amount just like everyone else but why should I when the service is unreliable. If it restarted maybe once or twice a day, I could live with that but several times a day is just getting out of hand. I can t tell you how many times I ve had people over and we watch something on Netflix and it just kills the movie randomly or when playing video games online and randomly get booted mid-game. First world problems, I know, but I pay for a service and if the service doesn t provide, why am I paying full price? I wouldn t pay the full amount for a half-eaten sandwich, why the hell should I pay full price for this?

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