Need to reboot Xfinity modem every 2-3 days to restore download speeds

Start with the modem's signal stats. Perhaps they already are, or they are close to being out of spec and intermittently they go completely of spec. Try getting them here http://192.168.100.1 or here http://10.0.0.1

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.

What is the exact make and model number of the modem ?

Thanks! 

The model of the modem is:   Voice and Data Modem Technicolor CGM4331COM   (the new white towers for gigabit).   However, I'm no longer able to sign into the modem.

Some back story, after posting this morning, I engaged support.  They looked at the modem, then said they would do an 'advanced reset' and to hold.  After 20 minutes, I realized we had gotten disconnected, and saw the modem was back online, but unable to access the internet.   After some checking, I determined they put the modem out of bridge mode, and as such, my network wasn't working.   I hard wired myself to the modem, was able to connect, but something changed the logon account for the modem (the default username and password no longer worked).   I engaged support once again, and finally they understood I needed to have them change the bridge mode back to enable.   Once done, I was again able to connect to the internet, however, I'm still unable to sign into the modem using the default admin/password, but they said they could not help me with that.   I have no idea if I'll need to reboot in 2-3 days, but at least I'm back online).

Any ideas on what the modem password may be if NOT admin/password, or how to reset so I can get those levels? 

Thanks!

Well, their 'fix' did nothing, and now less than 12 hours later, I'm back to 20Mbps down, and 41Mbps up...looks like time for another reboot....

Ok, found out how to reset the modem to reset the password and I'm in.   I'm not 100% where to find these setting but here:

Downstream was blank, until the very far right:

Here is Upstream:

I could not find signal to noise.

Thanks for your help!

I had opened another post, but starting a new one as it's 'down on the list' due to other issues posted.  🙂    At this point, just wondering how I can escalate this with Comcast support.   Since I upgraded to Gig speed tier (which required a new modem (Voice and Data Modem Technicolor CGM4331COM   (the new white towers for gigabit).   Everything will be fine until a few days, and the download speed drops to the 20's, however the upload speed remains constants (38-41).

I contact support, they put me on hold to check things, and then 'will do their magic' (meaning they reboot the modem), and things are back, despite telling them that I already do this to fix things.  The last call, they factory reset the modem and disconnected.  However, I have my modem in bridge mode due to my network, and had to get in to put things back as they were (somehow during this period, the default password got changed, but someone else helped me reset it so I could log in again).    

The weird part, is there's no download power levels show.  All the fields, except the 2 at the very end are blank.  (attached both downstream and upstream).   CM Error Codewords are all blank.

I'm back at this point again today, but need to wait until after work hours to call them (since my wife and I work from home (the reason we went to gigabit speed tier), and I can't have them disconnect her during work), and I know once again, I'll call on my cell phone (fair service) since I'll lose the home phone during reboot, wait on hold, explain my issue, and have them once again reboot the modem and tell me I'm all set.

Thanks.

The upstream power is on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Be advised that this may or may not be the root cause of the problem (YMMV). But it needed to be addressed regardless. Please post back with how things turn out.

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@neonate wrote:

 The only thing other thing I could think of after reading your question if it was possible to reduce it down to a 2-way splitter, would be to swap it with a 2 way splitter, one to the modem and one to a 3-way splitter for the cable boxes.

 

Any reduction of the cumulative losses is a step in the right direction !

 

I can check the levels after I reseat the center connection, should I power cycle the modem at that point 

 

Not necessary.

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Thanks for the reply.

The line from outside is connected to a 4 way splitter (installed by  Comcast).   1 goes to the modem (about 5 feet from where the line comes in), and the other 3 are run to the cable boxes.    The splitter is an Antronix, 4-way splitter 5-1000Mhz CMMC2004H.

All connections are tight (been checking the modem one), but I have not taken off the one from outside and reseated it (just verified it was connected tight).  I'll do that once my wife finishes work for the day.   The only thing other thing I could think of after reading your question if it was possible to reduce it down to a 2-way splitter, would be to swap it with a 2 way splitter, one to the modem and one to a 3-way splitter for the cable boxes.

I can check the levels after I reseat the center connection, should I power cycle the modem at that point (I know it will increase the download speeds, but so far, it hasn't changed the upload power levels or the download power levels)

Thanks!

Thanks.  Just ordered a Antronix CMMC2002H splitter (5-1002Mhz) and should be here on Sunday and I'll make the changes.

Understood, but I agree that if we can get things better situated, then it's worth trying.

Thanks again for the help.

Good luck with it !

Ok, I finally got all the pieces and moved everything around.   It's not the outside line to a 2-way splitter:  One going to the modem, and One going to the 3-way splitter which feeds my cable boxes.    I had to reboot the modem to make the swap, so I don't know if this solved the issue, but I now see that the values of the upstream have dropped, and there is now values under the downstream, that I didn't before (everything was blank).  I can't seem to capture everything in one snap since it is a scrolling window, but I've attached the new download and uploads.

Does this look more in line with what it should be?

Thanks for the help!

The stats are good now ! Bottom line. How are the speeds now ?

The speeds are within what I'm expecting for both up and download (realistically, I have the Gig service (download), but that's in a perfect world, so I'm not expecting those exact speeds).  However they always are after a reboot.

The real test will be if I don't drop down to the 20's for download speed in a few days.   I am encouraged by the the fact that downstream levels are now registering and your saying that the upstream levels are where they should be!     Hopefully in a few days I'm reporting everything still working great and can mark this one as solved.

Thanks to everyone who's been helping.   🙂

-stephen-