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Why is My Connection Often Dropping?

13K views 54 replies 5 participants last post by  e38BimmerFN 
#1 ·
My Comcast Xfinity connection has been very unstable for months now, losing connection many times a day. When the connection drops, the lights on my modem go nuts. Most of them start blinking. The disconnection can last anywhere from a few seconds to ten minutes.

I know it's not the modem or router, because both are new, and the issue has been happening with both old and new hardware here. Also, the new modem/router is from Comcast itself, and its firmware has been updated only days ago. I also know it's not an issue of interference, because even when a device is right next to the modem/router it will still get disconnected. Also, because the modem/router's lights go nuts,that doesn't strike me as an interference issue. Furthermore, every device on the network disconnects, so it's not any single device.

The only things I could imagine it is at this point are a bad coaxial cable, or something on one of the devices in the network is messing with the modem/router. If neither of those prove to be the issue, I have no choice but to consider Comcast itself at fault.

Any help would be greatly appreciated.

I'm on Windows 10, latest version.
 
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#12 ·
I'll try to remember to do that when it happens next. Do you think Port Forwarding/Mapping may be causing a problem? Whether or not I'm playing a certain game there are cycles/drops, but when I'm playing a certain game the frequency seems to increase. Specifically, if you look at the log, a few places where the disconnect occurred was when I was playing the game. The disconnect happened during one of the "delete port mapping" events.
 
#14 ·
Looking at your levels some more, I find it slightly unusual that all your upstream channels are only bonding ATDMA. That with the slightly high upstream power levels make me think that if it is a sync issue (internet/globe light) then that would be my first suspect. Also look under Troubleshooting > Logs for Xfinity/Comcast logs. I assume it's one of the other log types under the drop down but I can't find documentation. Looking for anything that mentions transmit errors (T1,T2,T3,etc). Edit out any MAC addresses if concerned with privacy.
 
#15 ·
Okay, the connection dropped twice this morning. The first time I was able to get a screenshot requested, but the second time the network disappeared altogether. I couldn't even log on to the modem/router to get a shot!

I did, however, get a copy of all three of today's logs. (I didn't realize there was more than one kind.)

Everything is attached.
 

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#16 ·
Yea, something is funky going on with those signal levels I think, however it looks like Comcast removed the gateway from logging it's HFC(modem) issues. It only has logs of it's router/firewall events. It "could" be an issue with the gateway rebooting because of a firewall issue, but I suspect they are more part of the normal process when the gateway reboots itself to re-acquire the connection. I suspect you will need to call Comcast to have them have a look, but we can troubleshoot until then. Would be good to get your upstream down a few dB. Do you have any splitters you can bypass between the coaxial on the street and your gateway? Can you describe the path the coaxial takes to get to your gateway?

When you call Comcast, ask if they see escalating T3 errors from their end. Also have them check your Upstream(US/TX) Signal to Noise Ratio (SNR). Finally have them ping your gateway from there and ask if they see packet loss.
 
#17 ·
Just as I was about to post this reply the connection dropped for the fourth in the last 90 minutes! You know, making things even more of a mystery is the fact that things get better for some weeks, then worse, then better... it's just gotten into another bad phase, apparently.

I have no splitters, no. I'm not even 100% sure what you're talking about, either. XD

The coaxial is connected straight to the wall, and then connects straight to the Arris modem/router. It's a fairly short cable as well.

As for Comcast, I don't hold out much hope that I'll get anything from them. I've called them about this before, and they say everything "looks fine" on their end. They rebooted my modem and hung up. o_O
 
#18 ·
Comcast is a cable company, so their service is delivered by cable, AKA coaxial, from telephone poles or underground wiring in the street. There is some where in your house where the coaxial enters your house from the street and then finds some way to the room the gateway is. If you don't know anything about it then your stuck with getting Comcast to come out and troubleshoot it, just be warned unless you isolate all your inside wiring, there could be a charge.
 
#20 ·
Really should have a Docsis 3 not 2 modem.

In post #10 we see channel bonding. In post #15 we see only one channel.

Problem is on Comcast's end. But then you write "but the second time the network disappeared altogether. I couldn't even log on to the modem/router to get a shot!"

That is an equipment [modem/router] problem.

Highly suggest you buy your own Docsis3 modem and router as separate units. It will save you $7 to $10 a month in rental costs and you have direct control/troubleshooting over the equipment.
 
#21 ·
FYI it is a DOCSIS 3.0 modem. That is why it has multiple upstream and downstream channels. The DOCSIS 2.0 refers to the channel width used for upstream. I know it's confusing, but it isn't referring to the modem. In picture 2, it's loosing channel bonding, but that could be the normal part of rebooting. It has to connect to the CMTS first on the default downstream channel to get the file that tells the modem which frequencies it can bond on.

I agree getting a stand alone modem is 100x better. Not only does it make it easier to isolate modem problems from router problems, not only does it give you access to better hardware, but it allows you to get your own router and not have to depend on the ISP for firmware. However, considering since your device is a phone wireless gateway, you probably get it for free as part of your phone service.

Speaking of which, do you lose phone service when you lose internet service? If so, that isolates it from any router problem, since the phone doesn't need the router portion to work.
 
#22 ·
Well, if it's a problem with the wiring in my home or locale, a new/different modem or router, or switching the Verizon, isn't going to fix the problem. I guess my best bet right now is to get Comcast to do something more than look at some numbers on a screen and tell me everything looks fine. Question is, how? XD
 
#24 ·
If the phone is dropping too, then it's a signal issue. The next step is to find out how the coaxial gets through your house to that room. Does it go through basement? Attic? Does it use splitters or a amp? What kind of wiring is it(RG6,RG59,etc). The main cable should connect to your house where the electricity does. From there, you can follow it with your eye. A Comcast tech can do this, it just may cost money unless you have the wire protection plan. However even if a technician doesn't come out, Comcast can troubleshoot remotely. Most comcast reps are outsourced though, so most are dumb as bricks. Ask them if they know what a T3 error. If they don't, ask for a Tier 2 rep or supervisor.

Also, technically speaking, switching to FIOS would possible fix the problem. FIOS uses fiber from the pole to your house, and then you can run ethernet from the FIOS modem (ONT) to a router, either one of theirs or one from a store(Walmart). This would bypass all the coaxial wiring in your house. I would say it's a "nuke the site from orbit" kind of solution, but it's a possibility. Is FIOS banging down your door with deals? Is switching something you are seriously considering?
 
#25 ·
If I can't get this fixed then switching is something I would definitely do, assuming it uses a whole different system as you described.

My modem/router is on the second floor (of a house). I don't know anything about the wiring. I guess I'll have to check.
 
#26 ·
Here is a blog that gives a simple diagram of how the coaxial wiring might be run in your house. There are two different ways, depending on the age of your house. Also, it's important to check the splitters to make sure they let the right frequency in. Comcast uses 5-1000Mhz. I have a feeling something (don't know what or where) is blocking the lower frequencies, which the modem uses for upstream, causing it to "choke" sometimes.

I also think it has something to do with load balancing, which is when the modem will reset to try to find frequencies on the cable that aren't under as heavy load by other Comcast customers around you. The way cable broadband is designed, the signal has some "pillow" or tolerance, and if your signal levels are bad in some way, natural variation of that signal (weather, wind, power spikes, etc) can then drop you below that tolerance, and you suffer the disconnect. I say this to try to explain how you can have a constant wiring problem and only see the symptoms once in a while. With that said, we don't know yet if that wiring problem is inside your house. We are just checking to rule it out as a possible problem. Once it's ruled out you can call Comcast with more authority, since then they will have to rule out their wiring. Their wiring stops when it connects to the electrical ground of your house.

Speaking of which, if/when Comcast comes out, have them check that your cable wire from the street is connected to your electrical ground. If not, it increases the likelihood of the cable picking up interference and be protected from any electrical surge over the comcast system. See here for a thread discussing the problems if not grounded.
 
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