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Strange Cable Connection Issues

Greetings cable modem gurus. I have had a strange experience, and I'd like to know what you guys think about it.

Over the past few days my Internet has been going down quite a bit, usually staying down for about 5 - 10 minutes on average.

Last night the Internet went down, and was still down today. My ISP reported no outages in the area, and checking my modem logs showed that acquiring a downstream channel and obtaining upstream parameters were both successful, but it would always hang on upstream ranging, and stay there until the modem would reboot and try again.

I had already turned the modem off and on before a few times, but on a whim, I turned the modem off, unplugged the cable from the wall, then turned it back on. It turned on fine but of course couldn't acquire any signal of any sort. Then I turned it back off, plugged the cable back in, turned it on again, and it connected just fine. Then a few moments later it went down again but reconnected just fine right away, then a few minutes after that it went down again and reconnected right away again, and it's been solid since, perhaps going on 20 minutes now.

Any ideas on this strange behavior? A bad modem or something else? Thanks!

You Gotta Love It
Mableton, GA
Maybe not as much as a bad modem but you may have connector issues or line problems. check your connectors and make sure they are tight both at the modem and demarc. May need a tech visit to check connection to tap.

Hope this helps.

reply to techconcern
Your downstream signal is most likely "ok" so the modem is locking downstream, and getting the upstream parameters, which is just telling the modem where to lock and at what level... The modem is unable to lock on that freq. You can move the modem to a different outlet, try where the cable first comes in, if that does not get you online, you'll need a tech. If it does get you online post signal levels from



1 edit
reply to techconcern
It happened again, where the connection went down and it locked downstream but wouldn't lock upstream so I unplugged / re-plugged the coax again and it was able to fully lock on and connect again.

Then I was poking around the forum and saw that some other people have had trouble with their upstream not locking in the past, and that they too unplugged and re-plugged their coax to get it working again. Interesting.

Anyhow, to the best of my knowledge since unplugging and re-plugging a few hours ago it's been working ever since. Here are the current levels and info:


Frequency: 585000000

SNR: 39.1

Power: 5.6


Channel ID: 3

Frequency: 23300000

Power: 49.2

The physical layout of the system is the coax goes straight from the wall to the modem using an about three foot cable. No splitters or anything.

In general if power cycling the modem gets it back online right away, everytime, it is a bad modem.


There have been a few times where the modem has had to cycle through its boot sequence a couple times before it would connect fully, and once it wouldn't get an upstream lock for hours until I finally unplugged and re-plugged the coax and then it did, but every other time once it drops the connection it goes through its boot sequence and reconnects on the first try.

The strange thing is, all day today it's been completely solid, then tonight it's suddenly started acting up again.


Kansas City, MO
reply to techconcern
What are you signal levels like?

Jump into the cable modem if you can (usually at » and check your upstream and downstream signals and signal noise levels... jot them down.

Then jump in when you are having the problems and jot down the signal levels and signal noise levels... present that information to your cable company and they should be able to fix it (assuming its not the cable modem itself).


Monroe, MI
reply to techconcern
Check your signal periodically to see if there are any wild variations. Could be a flaky modem, but I'm betting on an intermittent signal issue.

Cool Cat
Happy Valley
reply to techconcern
Please post your Log Entries.
What is the Make & Model of your Modem?

Since you are using a D2 modem or less & Time Warner has rolled out DOCSIS 3.0 utilizing Bonded channels, D2 modems can have issues when the Upstream slides above 49 dBmV. It will lose its lock on a channel & try to lock onto another. Of course this means connection issues. I see this more & more with D2 modems in a D3 network when your signal levels are at the top end of preferable. Just know that the modem in this scenario is not a "bad modem", it just can't function efficiently especially at that signal level.
In God we trust; all others bring data!