Forum Thread

Comcast internet not working - speedtest starts off 10Mbps then tapers to <0.5Mbps and doesn't complete. What gives?

Crew 568 434 January 4, 2016 at 10:47 AM
Need some help!

I have tried with a few routers, including the Xfinity equipment, and each of them are capable of the 150Mbps+ that I am paying for, but I can't maintain a consistent connection. I do not think this has anything to do with "peak" times, as it's been all over the place when it happens.

It seems that, randomly, the connection will be very slow, and when running speedtest (Ookla), the value jumps up and then gradually and continuously drops to near non-existent speed. This is something I just can't understand. If it's slow, fine. If it's fast, better. But starting up and then slowly dropping off until it approaches zero? I don't get it.

When I chat Comcast, they resend the signal, and all appears to be well (running several different speedtests), but the signal drops again later. I want to connect the ethernet cable to my router, which I've used successfully before, but if the connection isn't strong, the router isn't any help.

I can't seem to get a stable enough connection to have my router work reliably, so I'm really at a loss.

Anyone have history with this? Would like to try things on my own before having a service tech come out. =( I have tried manually resetting every piece of equipment, including unplugging and removing all connections and reconnecting.

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#2
Keep bugging comcast. Phone calls are probably better than chat. Fastest way to get this resolved would require them to send a technician.

Keep track of your speed test results with date & time in a spreadsheet. You can access a modem status page at 192.168.100.1 look at the numbers for signal and errors. Keep track of this information somehow, possibly in the same spread sheet.

Always try simple things like replacing your ethernet cable.

When it's working what speeds do you get? What % of the time is it problematic?
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#3
Quote from jkee View Post :
Keep bugging comcast. Phone calls are probably better than chat. Fastest way to get this resolved would require them to send a technician.

Keep track of your speed test results with date & time in a spreadsheet. You can access a modem status page at 192.168.100.1 look at the numbers for signal and errors. Keep track of this information somehow, possibly in the same spread sheet.

Always try simple things like replacing your ethernet cable.

When it's working what speeds do you get? What % of the time is it problematic?
I agree with everything said here. Call, be nice and polite, No one wants to help a jerk. Present the data you have gathered. Ideally you want a technician to come out, test the line with their higher end diagnostics. It's possible the line needs replaced, the ends need replaced and or you need a different comcast equipment.

Try a different computer to rule that out, as well as connected directly to the modem (no router) and see if any of that makes a difference.

You can signup for an account on http://testmy.net/ and have it run a test every 15min for a day or whatever you set.
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#4
Jkee and LiquidRetro, thanks for your replies! Rather than quote you both, I'll try to answer everything in one go.

Phone calls are better than chat, yes, but I get spotty service in my basement where all of my equipment is, unfortunately. I am always polite (not just saying that; I know it's not THEIR fault), and they're usually very helpful.

I have tried multiple cables and different computers, as well as updating my ethernet drivers and resetting the adapter on my laptop.

I have had success plugging ethernet directly from the modem to my laptop, but even this isn't reliable. It was working great as soon as I had Comcast reset the signal, but later that day, it was doing the "falling numbers" thing. It's just so strange that it's happening with both modems, and the TP-LINK TC-7610 is literally brand new; I purchased it from Jet about a week before Christmas.

When it's working, my speeds are phenomenal. I can get just shy of 180Mbps down, on wired and wifi testing (phone app) through Ookla, and around 15Mbps upload, but never higher than that. When it's not working, it's hard to even gather data, because the "falling numbers" for my download speed literally do not allow the test to complete. Very frustrating.

Good call on "testmy" - I'll have to check that out.

Thank you! I'm going to reset everything and call Comcast tonight. I'll keep you posted.
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#5
Comcast also has its own speedtest [comcast.net]; I'd *think* that their test communicates with Comcast servers whereas the Ookla one is out of the network. It would be interesting to see if the behaviour on the 2 is different (e.g. does the Comcast one work all the time?)

What's the other modem you've used? (you only mention one by a specific model #)
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#6
Quote from Dr. J View Post :
Comcast also has its own speedtest [comcast.net]; I'd *think* that their test communicates with Comcast servers whereas the Ookla one is out of the network. It would be interesting to see if the behaviour on the 2 is different (e.g. does the Comcast one work all the time?)

What's the other modem you've used? (you only mention one by a specific model #)
Thanks Doc. Sixers fan?

I have attempted to use the Comcast test (as linked by the chat rep), and when reset signal, I was getting the same speeds as Ookla (I was doing Ookla as a backup test, but I think they sponsor the Comcast test). The Comcast speedtest does NOT work all the time; in fact, I was having trouble getting it to function (the flash portion, anyway), when Ookla was moving slowly.

The other modem I've used is the Comcast equipment, docsis 3 residential combo modem/router. I think this is it: http://www.amazon.com/Residential...B00NR1EHP8

I've had better success with the Comcast gear, but the ethernet-only connection was working on the TP-LINK last night, when the signal was reset.
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#7
Quote from Crew View Post :
Thanks Doc. Sixers fan?

I have attempted to use the Comcast test (as linked by the chat rep), and when reset signal, I was getting the same speeds as Ookla (I was doing Ookla as a backup test, but I think they sponsor the Comcast test). The Comcast speedtest does NOT work all the time; in fact, I was having trouble getting it to function (the flash portion, anyway), when Ookla was moving slowly.

The other modem I've used is the Comcast equipment, docsis 3 residential combo modem/router. I think this is it: http://www.amazon.com/Residential...B00NR1EHP8

I've had better success with the Comcast gear, but the ethernet-only connection was working on the TP-LINK last night, when the signal was reset.
Take your router out of the loop right now. It just adds to the equation and you need to make things easier to trouble shoot. I still am in favor of seeing if you can get a technician to come out and get comcast to replace their equipment.
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Quote from LiquidRetro View Post :
Take your router out of the loop right now. It just adds to the equation and you need to make things easier to trouble shoot. I still am in favor of seeing if you can get a technician to come out and get comcast to replace their equipment.

Indeed. Modem and hardwired PC/laptop, period. Especially since the modems have been changed, I'd suspect something on their end. I can't imagine hardware (physical wiring, etc) being a problem here though.

I had an intermittent connectivity issue with Comcast several years ago when I lived in a condo. The culprit? Ancient equipment in a network box that looked like a rat's nest. They eventually replaced the whole box and equipment but not until after I'd already moved on to ATT.
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#10
Quote from LiquidRetro View Post :
You can signup for an account on http://testmy.net/ and have it run a test every 15min for a day or whatever you set.
So, I gave that "testmy" test a shot, and ended up with 42Mbps.

That's noted as higher than almost all the other averages, and while the other tests are still showing the tippy-top results (180Mbps), I think the other test might be more accurate using random data packets.

Anyway, now that I'm showing decent speeds, I'm going to attempt to reset my router and try and get that on a different channel. I will keep you guys posted - thanks again.
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#11
Quote from Crew View Post :
So, I gave that "testmy" test a shot, and ended up with 42Mbps.

That's noted as higher than almost all the other averages, and while the other tests are still showing the tippy-top results (180Mbps), I think the other test might be more accurate using random data packets.

Anyway, now that I'm showing decent speeds, I'm going to attempt to reset my router and try and get that on a different channel. I will keep you guys posted - thanks again.
Router channel should not matter to a wired connection. Also you can scan with apps for your phone and find a clear channel.
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#12
Alright, so I got home last night and unplugged the router, and connected the ethernet directly to the modem. Works great, on both Comcast and Ookla tests, as well as decent speeds on TestMy.

Plugged the router into the modem via another ethernet cable, different port, and wifi was working great. TestMy showed excellent speeds on 3 different mobile devices.

I have not run an ethernet cable directly from the router yet, but since this is working, I'm not going to mess with it.

My brother ran TestMy intervals last night on his wired connection, and again today, so we'll check those and report findings. I am hoping to be able to, at some point, get my TP-Link modem working properly, hooked up to the router, and run all ethernet cables from there, so I can be rid of Comcast equipment altogether, which is why I bought this new modem.

I'll keep you guys posted! Thanks!
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#13
Quote from LiquidRetro View Post :
I agree with everything said here. Call, be nice and polite, No one wants to help a jerk.

Try a different computer to rule that out, as well as connected directly to the modem (no router) and see if any of that makes a difference.
Kind of hard not to be a jerk when dealing with Comcast. Big Grin

Agree with different computer. I've had many odd software related speed issues. Latest one was related to Avast slowing the crap out of Chrome.
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#14
Glad you got it figured out, testmy.net has a few options as far as where it will run it't test the Comcast one is usually optimistic and Comcast and others have been accused of giving speedtest web sites priority to give better results. Testmy will also show you a graph which is also very handy.

You should only talk to/complain to Comcast when your computer is connected to the modem itself and usually you can log into the modem is view mode to see what channels are working and some other status doing that could also help with the diagnostics.
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