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Sun Mar 28, 2021, 01:11 PM

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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Reply Need some help with a DOCSIS 3.1 cable modem (Original post)
MerryHolidays Mar 28 OP
discntnt_irny_srcsm Mar 28 #1
MerryHolidays Mar 28 #4
discntnt_irny_srcsm Mar 28 #8
Hugh_Lebowski Mar 28 #2
MerryHolidays Mar 28 #5
unweird Mar 28 #3
MerryHolidays Mar 28 #6
cayugafalls Mar 28 #7
MerryHolidays Mar 30 #9

Response to MerryHolidays (Original post)

Sun Mar 28, 2021, 01:31 PM

1. Are you adverse to using (or maybe learning) a bit command line? n/t

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Response to discntnt_irny_srcsm (Reply #1)

Sun Mar 28, 2021, 01:39 PM

4. Not at all!

Any thoughts there would be great.

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Response to MerryHolidays (Reply #4)

Sun Mar 28, 2021, 04:10 PM

8. Open a command line window...


Type at the command line: ping

The ping command sends a short message to the specified host and asks for a return message.

When the internet drops out ping the modem (which should be visible).
If you can see the modem and not the web, it's comcast. Ping will say "Reply..."
If you can't see the modem, it's your LAN, maybe the mesh router. Ping will say "Request timed out."

It's probably the comcast service. That's my guess.

Now before you get into any of that have you replaced the Ethernet cable between the modem and router?

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Response to MerryHolidays (Original post)

Sun Mar 28, 2021, 01:34 PM

2. I would just switch it to Arris and see what happens ... why not?

Or You might just rent an Xfinity one for a month, see if their own modem has the same issue. It's not like it's that much to invest.

I have an Arris 3.0 Docsis w/Linksys mesh, and it's been fine. Every issue has been with the signal coming into the house (cause Cox kinda sucks) thus far.

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Response to Hugh_Lebowski (Reply #2)

Sun Mar 28, 2021, 01:41 PM

5. I am going to pick up the Arris at a local store in an hour or so

My family will yell at me (!) if the internet is down too long, so I am going to try to do the switchover this afternoon when, hopefully, no one is around.

And yes, renting the modem from Xfinity is a good idea. Xfinity sort of washes their hands on problems when you're not using their modem. That being said, they are helpful. While they claim they are not the problem, I do wonder. Getting the Xfinity modem for a bit would force them to work on the issue if it's on their end.

If the Arris is also a bust, that's my next step.

Thank you!

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Response to MerryHolidays (Original post)

Sun Mar 28, 2021, 01:35 PM

3. MB8600 On Comcast Checking In

User here and also bumped up to their gb plan. I see stalls at times that I suspect are Comcast. My suspicions are based on spontaneous recovery and the short lived nature of the disruption with no action taken to resolve it on my end. And also the slowness of an Ookla app to find a Speedtest host when it occurs.
No tool suggestions other than Ookla but my use of it is while experiencing a transient network stall to see if it can resolve host lookups. Iím going to follow this thread to see if anyone else can share better advice.

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Response to unweird (Reply #3)

Sun Mar 28, 2021, 01:46 PM

6. Our drops seem to last a bit longer

My daughter got booted out of an online class for around 7 minutes. I wasn't at home then and could not trace the issue.

Early this morning, the internet dropped on me for about 2-3 minutes.

I like the earlier idea of renting the Xfinity modem for a short while (if that's possible) and forcing Xfinity to address the issue if it's on their end.

To be honest, though, our problems seemed to arise with the new modem and the switch to the Xfinity 1gps plan. It's very likely one or both of those. However, I'm no network engineer, so I clearly can't say for sure.

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Response to MerryHolidays (Original post)

Sun Mar 28, 2021, 02:32 PM

7. I use Comcast Business Class internet. I currently use the rented modem and they upgraded

me to the new Docsis 3.1 version. It is spendy and I am thinking of getting my own, BUT, we need constant speed and support and the amount of horror stories, drops and issues with 3rd parties on Comcast/Xfinity kind of make me hesitate when pulling the trigger.

If we did not run 3 businesses out of our home this would be a no brainer, but...

I don't need Comcast getting all corporate overlord on me and booting my modem for spite...

Perhaps they are on the up and up, I just hesitate to to take the chance.

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Response to MerryHolidays (Original post)

Tue Mar 30, 2021, 12:05 AM

9. Thanks for all the great ideas here: An update

Last edited Fri Apr 9, 2021, 06:04 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!

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