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CM1150v Intermittent Slowness and Channels not locking

GSquared
Aspirant

CM1150v Intermittent Slowness and Channels not locking

Hello,

 

Having an issue where the CM1150v modem I have went from perfectly fine to all of a sudden flashing the downstream light repeatedly. My speeds went from 300+ to about 20-30mbps. It's been intermittent where one day it is fine, and the next it is blinking all day and slow as can be.

 

The coax line was reading 1Gbps+ on Comcast's line test, but this is when the modem also stopped flashing the downstream light and was working fine.

 

All downstream channels are locked except ID 28 when this happens, with an OFDM locked as well. 4 US channels locked. (28 is locked when it is not happening.)

 

Modem: CM1150v

Firmware: v2.02.04 (LAG disabled)

 

Thanks for any help you may be able to provide!

 

 

Model: CM1150V|DOCSIS 3.1 Nighthawk® Multi-Gig Speed Cable Modem for XFINITY® Voice
Message 1 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

Do you have a screen snip of your modem connections page?

If you directly connect to the modem, what speeds do you get? Remove the router so we can make sure its a modem issue and not a router issue. 

I'd also recommend removing any splitters, amplifiers, 90 degree elbows, extended coax runs. Check the connections to make sure they're tight. Also check your cables. Worn, corroded, bent, or cables with moisture within them can all causes intermittent connection issues. 

Message 2 of 16
GSquared
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

Yes, here is a screenshot of when it is not working: https://i.imgur.com/7vPL1py.jpg

 

In addition, I already had Comcast techs out to the house who blamed the modem. We tried directly from the modem using cat7, same thing. It's not a router issue at all. The coax was reterminated by the Comcast techs and the cat7 cable used was brand new out of the package when trying the direct connection with the same results. There are no splitters besides the main MOCA one splitting the main line through the home.

 

Direct connection: ~30mbps when downstream light is flashing, 300+ when it is not.

Model: CM1150V|DOCSIS 3.1 Nighthawk® Multi-Gig Speed Cable Modem for XFINITY® Voice
Message 3 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

You have a lot of errors in your line. And you're directly connected to where the cable enters the house with no splitters? I'd have them check it again and have them hook up one of their modem only devices if they're blaming the modem. It potentially could be the modem but with that many errors, I'd be inclined to think its something from their box to your house. 

You also didn't capture you ofdm channels. Thats the key for gigabit. 

Message 4 of 16
GSquared
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

They hooked up their tester device, the XM2(?) to the line and tested it. They got over 1gbps on their device and when plugging the modem back in, the modem was working correctly at that time as well. An hour after they left, it was back to the 20-30mbps. A day later, it was back up to normal speeds, then a day after that continuing to now, it is back at 20-30 mbps. It's only when the downstream light is flashing and that channel isn't locked that this happens.

 

The cable goes into the house, then splits to the TVs and the modems using a MOCA splitter (they just put this in replacing a powered amplifier). This line goes directly from that house splitter to the modem.

 

Comcast keeps wanting to blame the modem and the tech said please replace that modem before calling us back out.

 

I don't have gigabit yet, was going to upgrade in the future. Only have about 350mbps. I'll try to capture that section when I get home.

 

Here is when it is working: https://i.imgur.com/ynacZ9j.jpg

Message 5 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

So when they're there and its directly connected it works on your modem and on theirs. Then they unlook it and add the splitters/moca adapters (why moca?) and now it has issues. 

If you absolutely need the splitters it should go like so:

incoming line--- a 2x port splitter with one connection going to the modem and then other to the rest of your tv's/splitters/moca adapters.  The modem is more sensitive to problems than what your tv's/moca adapters are. So it should be first in the line and only on a 2x port splitter. You can add splitters after that to run the rest of your device but the modem should have its own dedicated line.

If you are directly connected to the line coming in without the splitters/adapters/etc, do you get gigabit?

Even when its running well, you still have a lot of erros. 

Message 6 of 16
GSquared
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

Not exactly, let me try and give a timeline:

Bought modem in May, worked until a week ago. Don’t know what the errors looked like prior to this.

Modem starts flashing downstream light a week ago and notice download are going excessively slow. Speed test reads 20-30mbps depending on the run.

Tech comes Saturday. Modem still flashing downstream. Show tech it’s flashing and that one of the channels isn’t locked including the page with the errors on it. He states that all the information showed us normal, proceeds to check lines from their box, into the house, and to the modem. All lines check out according to the tech. We wait about 30 minutes for an additional tech with the testing tool. During that time, he swaps our powered amplifier for a MOCA splitter (his words) to feed the whole house more efficiently and without an additional point of failure in the form of the powered amplifier.

Additional tech arrives, connects cable, has trouble running speed test. Disconnects coax from modem. Line reads 1gbps on their test device. Plug the cable back in the modem and downstream stops flashing, modem is at correct speeds again. They leave.

Hour later: flashing downstream and low speeds.
Next day: full speeds
Day after: flashing and low speeds


This setup has worked great until a week ago with our correct speeds and has been like this for years, just had a Comcast modem until this past May.

My direct line is in the attic and I don’t have an Ethernet cable long enough to reach my desktop if I put the modem in there to test it unfortunately. I don’t have any portables with one either. I suppose I can buy an adapter for my laptop and try it out connected directly to the main line.
Message 7 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

The reason I think its the cable or how you've split the signal on the cable is, for the most part, modems either work or they don't. There's not a whole lot of in-between when they go bad.

You must have coax where the modem is. But you have a bunch of devices connecting in between where the cable comes in and where the modem is. Remove them and just run a direct connector (https://www.amazon.com/Connector-VCE-Extension-Adapter-Connects/dp/B01F54KYO2?ref_=fsclp_pl_dp_1) without the splitters/amplifiers/etc. See if it works then. The cable company is only required to get a good signal to your house. After that, if you add a bunch of splitters/moca adapters/poor/cheap cables then its on you and they aren't required to do more. 

So your goal is to see if it works when it enters your house. If it does, it isn't the modem or the signal coming in, its everything you introduced after it enters your house. 

Message 8 of 16
GSquared
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

They put in all and any splitters that are in the home to ensure service is provided to their equipment in the rest of the home. All of the splitters or amplifiers are theirs and they put them in. I am still in contact with them to try and figure this out but I was curious if it was something known on the modem as I saw that speeds were dramatically decreased with LAG enabled on this firmware. (It is disabled on mine, but I would like to enable it.)

 

I will try and figure out getting a direct line going to the modem, but like I said, all the splitters and adapters are all Comcast's equipment that they put in. They guarantee the service to all the devices in the home, and that's how they acheieved it. Like I said though, this setup had been working alright for quite some time now and it just started acting up a week ago.

Message 9 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking


@GSquared wrote:

They put in all and any splitters that are in the home to ensure service is provided to their equipment in the rest of the home. All of the splitters or amplifiers are theirs and they put them in. I am still in contact with them to try and figure this out but I was curious if it was something known on the modem as I saw that speeds were dramatically decreased with LAG enabled on this firmware. (It is disabled on mine, but I would like to enable it.)

 

I will try and figure out getting a direct line going to the modem, but like I said, all the splitters and adapters are all Comcast's equipment that they put in. They guarantee the service to all the devices in the home, and that's how they acheieved it. Like I said though, this setup had been working alright for quite some time now and it just started acting up a week ago.


Comcast doesn't guarantee anything once it enters the house unless you're paying some type of home service plan (not even sure if they offer that). They might help you out to get the tv working because its their signal but unless you use their modem, they don't care how they degrade the signal going to a 3rd party modem because they aren't responsible for it.  

And with your errors in your line and if they've truly said they won't come look without your replacing it, you're kind of limited. Here's your options.

1. try the direct wire solutions and see if it fixes the problem. If it does, its the way the line has been split and comcast just doesn't care.

2. replace the modem either by going through netgear to see if they'll authorize an RMA (if you're within warranty) or just buying a new one. If it still has the issues, comcast can't continue to blame it on the modem. 

3. Rent a modem from comcast for a month. If you get the same poor signal on their equipment, they can't blame in on netgear and will need to fix the signal. its usually $10-15 to rent. Some modems are more sensative to less to poor signal so even if it works, get a screen snip of the connections page for errors/signal strength.

Message 10 of 16
suspen
Guide

Re: CM1150v Intermittent Slowness and Channels not locking

Was this resolved for you? I am having the same exact problems you describe here except I don't believe our signal is being split before the modem connection. We also used to have Comcasts all-in-one modem/router before we switched over to this new setup. When we had that there was intermittent service from them but it wasn't as frequently down as it is now. Before I'd have to call in to Comcast to have the signal resent maybe every 2 weeks.

 

Were using Google mesh system as a router. We have 3 of those. For the first 2 weeks the whole system was up and running and we had the fastest internet I've ever experienced. Now same problem you are having, intermittent service or no service at all. I have to have Comcast resend the signal every day now. 

 

Same exact thing you describe above. The Comcast tech comes out. Everything checks out. They leave and something goes down a few hours later. Yesterday the tech left and for the first time my main phone line went down but we had internet. Usually its the internet that goes down after they leave. I wake up this morning and no internet. Restart the CM1150v and now internet is back but very slow. I've had a Comcast tech out 3 times in the past 2 weeks.

 

I'm not an expert but I don't think the CM1150v is playing well here. It appears other people are having the same problem. If this is a Comcast "recommended" modem why can't Netgear or Comcast figure this one out? We're wasting our time troubleshooting. This is so frustrating. I work from home so this is costing me money every day.

 

 

Message 11 of 16
plemans
Guru

Re: CM1150v Intermittent Slowness and Channels not locking


@suspen wrote:

Was this resolved for you? I am having the same exact problems you describe here except I don't believe our signal is being split before the modem connection. We also used to have Comcasts all-in-one modem/router before we switched over to this new setup. When we had that there was intermittent service from them but it wasn't as frequently down as it is now. Before I'd have to call in to Comcast to have the signal resent maybe every 2 weeks.

 

Were using Google mesh system as a router. We have 3 of those. For the first 2 weeks the whole system was up and running and we had the fastest internet I've ever experienced. Now same problem you are having, intermittent service or no service at all. I have to have Comcast resend the signal every day now. 

 

Same exact thing you describe above. The Comcast tech comes out. Everything checks out. They leave and something goes down a few hours later. Yesterday the tech left and for the first time my main phone line went down but we had internet. Usually its the internet that goes down after they leave. I wake up this morning and no internet. Restart the CM1150v and now internet is back but very slow. I've had a Comcast tech out 3 times in the past 2 weeks.

 

I'm not an expert but I don't think the CM1150v is playing well here. It appears other people are having the same problem. If this is a Comcast "recommended" modem why can't Netgear or Comcast figure this one out? We're wasting our time troubleshooting. This is so frustrating. I work from home so this is costing me money every day.

 

 


We're more than willing to help you troubleshoot but you need to start your own thread. We try to focus on a single person's problem to keep things from being confusing as well as each situation is unique and requires different details/approach. Again, please start your own thread so we can help you. 

When you start it list:

Modem speeds you pay for

Speeds you get hardwired

Screen snip of your modem connections page

router and firmware

What exactly is happening. Not just signal drops. Do wireless and hardwired, what fixes it, what is your wiring layout, etc. The more details the better. 

Message 12 of 16
coldcaffeine
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

Same problem here with a CM1100 and Comcast. 2.01.02 firmware. No signal splitter. My 250 Mbps connection drops to about 30 Mbps until I reboot the modem.
Message 13 of 16
FURRYe38
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

Have you had the ISP check the signal and line quality up to the modem? 

 

Might contact NG support and have them review any debug logs from when this happens. 

@vkdelta 


@coldcaffeine wrote:
Same problem here with a CM1100 and Comcast. 2.01.02 firmware. No signal splitter. My 250 Mbps connection drops to about 30 Mbps until I reboot the modem.

 

 

Message 14 of 16
GSquared
Aspirant

Re: CM1150v Intermittent Slowness and Channels not locking

Haven't had a chance to try the modem directly on the line that comes into the house (in the attic), but that still would be completely unreasonable to not be able to have internet service and TV service at the same time -- a splitter is neccessary to provide this and has worked for years, including months with this modem. (And they just replaced this piece when there for this service call) It just happened all of a sudden 2 weeks ago that the downstream light started flashing and speeds dropping. Not sure if firmware related or Comcast line related or what. They tested all the lines all the way up to the modem. It's just so itermittent that I don't know how to tell anyone from Comcast how to see it since it's working for a day, then not for a day or working for a morning, then not at night. It's completely random. 

 

This is still happening to me, the downstream light flashes and the speeds drop. The light stops flashing and the speeds go right back up. 

 

I'll try to report back after I have a chance to test it on the line coming into the house when the problem is occuring.

Message 15 of 16
FURRYe38
Guru

Re: CM1150v Intermittent Slowness and Channels not locking

Smiley Wink

Message 16 of 16
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