Need some help with a DOCSIS 3.1 cable modem
Hi All:
I need your guidance on my home network. I am on Xfinity internet and just switched to a DOCSIS 3.1 modem (Motorola MB8611) a few weeks ago. My family, which is doing videoconferencing for work/school, is complaining that we are now getting internet drops from time to time, and usually at the worst time. We are using a Google WiFi mesh router (and have been doing so for years, now).
When I got the new modem, I upgraded our Xfinity plan to the 1gps plan. Our speeds are amazing, but the intermittent drop in internet is not acceptable. Both the family and I need a constant reliable connection (as do we all), given that we will be attending work/school online for at least the next few months. Even after the pandemic nightmare subsides, I need a reliable connection for work.
I spoke to Xfinity customer service, and they see no problems on the cable line. I also spent HOURS with Google to see if there were any issues with mesh router. While Google was all over the place and not very focused, I did perceive that the router is not the issue. Based on the complaints from my family about dropped internet that occurred after I installed the Motorola modem late last month, the troubleshooting with Xfinity and Google, and logging into the modem and checking event logs on the modem, the only thing I can think of is that the modem is not working properly. I checked some reviews online, and several have complained about precisely the problem we're having with this modem.
I am thinking about returning the Motorola modem (I still have a few days left in the return period) and getting an ARRIS Surfboard S33 DOCSIS 3.1 modem as a replacement. It's not cheap, but over time, it is cheaper than renting an Xfinity modem. Regardless, I need a solution that works.
First question: are there any software tools that a non-network engineer like me can use to isolate/trace the source of the issues and problems? I would rather not return the Motorola without making sure, as best I can, that it is the source of our problems.
Second question: do any of you have experience with the ARRIS modem? I think I've read here that some have it. I am ok to get a new modem and replace the Motorola, but I don't want to go through the hassle if the ARRIS also has problems.
Any guidance you can give would be great and definitely appreciated!
Thank you in advance.
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Last edited Fri Apr 9, 2021, 05:04 AM - Edit history (6)
I installed the Arris yesterday afternoon, and there have been no complaints from the family about dropped internet since installation about 30 hours ago. They still complain about many things, but not internet. 
Speeds are fabulous.
I've been reading about Motorola modems. From what I gather, these modems are not manufactured by Motorola, but by Zoom Telephonics (not the same as Zoom Video). I've seen complaints about the MB8611 causing dropped internet, but let's see if that really was the culprit in my case. Assuming it was issues with Motorola, I'm lucky because the return window to give back the modem ends this week, so I'm not stuck. That was really the impetus to make the change from the Motorola to the Arris: I did not want to be stuck with a very expensive modem that was POTENTIALLY buggy, at least for me. Now, I have another 2 weeks to test the hell out of the Arris until its return window expires.
It's very early, but the Arris has been going strong more than one full day without failing. Hopefully, that's a good sign.
These modems are expensive, but Xfinity's lease option (for a combined modem/router) is something like $14/month. I already have the Google WiFi mesh router, so I'm not sure Xfinity's modem/router combination would work for me because I have a lot of area to cover where I need internet. I should get back my investment in a little over a year, and probably with equipment that is superior to Xfinity. The downside is, as mentioned earlier, Xfinity tries to cop out when troubleshooting internet problems if you don't have its equipment. However, I've found if you are a little bit pushy, but in a nice way, their telephone tech support is actually reasonably helpful and quite friendly. If they can't solve the issue, they are usually good about sending a tech to the house. With one very notable exception, all the tech visits I have had have been uniformly excellent. Luckily, I haven't had need of an in-home Xfinity call regarding internet since at least 2017, and I truly hope I won't need one for this issue.
If, for whatever reason, the Arris doesn't work out, as one poster suggested, I will rent the Xfinity modem to get their troubleshooting assistance and also examine the cables. Apparently, co-ax and ethernet cables, as pointed out by another poster, can be quite sensitive. I've been checking to make sure the connections are secure, as this is apparently the cause of many problems.
I am also learning a lot about DOCSIS terminology like T-3 and T-4 timeouts and corrected/uncorrectable errors while I monitor the network. I am logging into the modem every few hours to see if there are problems.
Will keep you posted!
On edit: we are now at 2.5 days with the new Arris S33 without a discernible drop in internet service. Luckily, I was able to return the Motorola MB 8611 and get a full refund. Fingers crossed, but it does appear to be that the Motorola modem was at fault. We have four videocalls going on simultaneously several times in the day, and there have been no issues with the Arris that we can see. When I log into the modem, I do see some corrected and uncorrectable errors, but my understanding is that these are not an issue unless they are an issue. Luckily, no complaints from the family.
On further final edit: Hopefully, this is my last post/edit for this thread. It's been nearly 2 weeks since I switched from the Motorola to the Arris modem. As far as I can tell, there have been no drops in internet (but I have not been monitoring 24/7; however, I've had zero complaints from the family about drops). Hopefully, I'm not jinxing myself, but it appears that the Motorola modem was the problem. I've learned a few lessons from this (besides underscoring the fact that DU is a GREAT place to get on point advice on tech and just about any other issue!):
1) Do your research - the problems with the Motorola and Xfinity's gigabyte service were well-documented by reviewers. In hindsight, several other reviewers had exactly the same issue I had with the Motorola.
2) Check ALL your connections, both hard and soft - thanks to the advice here, I tightened cables etc and pinged the hell out of both modems and ran as many diagnostic tests as I could on the modems, the router, and the internet service via Xfinity. There are tools out there available for free to help you do some diagnosis on your own, without having to be a network engineer.
3) Don't trust brand names - I originally bought the Motorola over the Arris because I had never heard of Arris and had heard of Motorola since I was a kid. Well, after doing some research (see point 1), I found out that was silly: apparently, Arris bought Motorola's technology a few years back, and Motorola's modems are actually made under licence by a company that is not Motorola. Brand names can be a useful indicator of quality and origin, but not always. Do your own research if you have the time.
4) Don't trust Amazon blindly - Putting aside the social issues with Amazon, which are legion, I am increasingly becoming distrustful of Amazon. I hadn't realized how many fake reviews are out there, but I now use some software that gives me an indication of whether reviews are fishy. Also, Amazon is NOT the price leader on every single item. I actually got the Arris from a local store on the same day cheaper than I could with Amazon with next day delivery, all in. Yes, I did have to drive a few miles to the store on a Sunday, but that was fine, since it allowed me to get the Arris installed and tested while the family was off the internet.
Amazon used to be my one-stop shop for all things technology, as I could see everything, compare everything, and have good reviews to help make my decision, along with getting great pricing. And for many years, that was true. However, I have become more aware of the rampant fake reviews on Amazon (but also elsewhere), and the fact that Amazon's online systems are nowhere near as good as they used to be, as they spend too much tinkering with search results to up or cross-sell you on other stuff, rather than giving me the bottom-line answer on what's the best for me based on my own needs. This, coupled with the social issues and the huge amount of excess packaging we get when getting stuff delivered, means that Amazon will be one of several places I check. If they don't fix their social/workforce issues soon, I don't mind dumping Amazon all together.
Anyway, this is hopefully the end of my saga with my new DOCSIS 3.1 modem!