Motorola MB8611 - Internet dropping/reboot - SYNC Timing Synchronization failure and No Ranging Response received - T3 time-out

@user_Es0824​ I do not think this is only Motorola issue. I've seen plenty of reports with similar issues from ARRIS users.

Awesome, before we begin can you confirm all the coaxial cable connections in the home should be "finger tight". Can you perform the following connection checks?

Check the coaxial cable at the wall plate?
Check the coaxial cable at the Internet device?
Adjust/remove splitter if applicable?
Ensure the device is located at the originally installed outlet?
Ensure any amplifier within the home (if applicable) is connected to power?

Let me know when this has been done, please?

Awesome, auto bots... See, you didn't even read my post. If you did you'd know that there is no problems with the cable or connections on my property. But that's ok, I signed up for 2 years contract and I will have to suck it up for another year. Btw, your direct messaging support hasn't been responsive for the past hour.

@user_Es0824​ Could you please check and post your modem software version?

Thank you for the update, @user_fd33c8. Please keep us posted on what you see on your end. 

@user_fd33c8​ This includes my connection page as well. The only answer I have is that they pushed through some sort of fix. 

@user_Es0824​ Thanks. Same version as I have and I had it for some time now. 

I haven't seen this issue yet. My software version seems to be older, though this modem is new as of about a month ago.

@user_fd33c8​  Also, when I had the issue (and still might but have been very lucky), Mine was dropping every hour. Sometimes every 15 min, sometimes every 5 min (after a tech visit), and sometimes every hour it would drop and my modem would restart. 

Hmm, didn't reboot yet. Up for 12h - that's a new record. Maybe lines are not busy yet because people still asleep after Ney Year celebration?

@user_fd33c8​ 

Why only notices show timestamp but not issues?

I dug into how cable modem initialization works, so armed with a little knowledge, here's what I believe. The TLV values that start with 84.x come from the configuration file provided by an Xfinity configuration server as part of the cable modem (CM) initialization after a power cycle or reboot. That file contains the configuration of the downstream (DS_Diplexer_Mode...) and upstream (US_Diplexer_Mode...) frequency bands and the channels within those bands. 

The official time reported by the CM in the log comes from the ISP's time server, but since the CM hasn't fully initialized, it hasn't yet received the time. It could report a time since the reboot, but it would likely be a delta from the Unix epoch starting with 0 (equivalent to Jan 01, 1970, at 00:00:00). (It appears that Arris S33 modems do that rather than having Time Not Established.)

I would be very curious if you have other log messages that mention something like CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-21.2, CMSTATUS:DS_Diplexer_Mode_Change_Ignored:TLV-21.3, and/or CMSTATUS:US_Diplexer_Mode_Change_Ignored:TLV-21.1, 85MHz. 

Xfinity is doubling the upstream speed for its customers, which is a good thing. However, they need to widen the upstream frequency band to make room for additional channels. That requires moving the downstream frequency range higher to leave a gap for the wider upstream frequency range. I think they are trying to reprogram the CMs from different manufacturers to do this, but the configuration is incorrect (or they have multiple conflicting configurations). There are (at least) two ways to configure those settings. One is in a "file" sent from an Xfinity server to the CM at startup. (That is the TLV-84.x values) Another is a message sent to the CM after startup. The message version is newer and may only work with DOCSIS 3.1-compliant modems. (That is the TLV-21.x settings.)

Now, let's enter pure speculation. My actual guess (WAG at that) is that Xfinity left the "file" version untouched so that older (DOCSIS 3.0 and earlier) modems would stay at the older settings, and newer modems would get the message to reconfigure themselves. The CM should make the changes needed for the increased upstream bandwidth and channels. However, I found a sentence in the DOCSIS 3.1 spec that says if that configuration is set in the file, it cannot be set using the message version. An attempt to do so should be considered an error. Some manufacturers may not have honored that (i.e., noticed) restriction, but the MB8611 does (as does the Arris SB33). If the Xfinity side believes that the reconfiguration has occurred, it may be commanding the CM to restart to get it to resynchronize. (It is also possible that when Xfinity's server realizes that the reconfiguration failed, it restarts the CM to get it back to a known state [to try again].) This is just a guess.

I'm in the northern Virginia area and not seeing this yet. I would be interested to know where the customers having this issue are geographically located (roughly so as not to disclose any PII). The rollout of the increased upload speeds was supposed to start with a test area. I'm guessing I'm not in that area, but those having those issues are.

Interesting. I see only TLV-84.x records, no records with TLV-21.x. Btw, my modem is still going since last night. 16 hours so far. Something indeed must of happened on Xfinity's side. 

@petmitsu​ I doubt it's modem. Now it's working fine for 16 hours when for the past few months it would drop internet and reboot 3-4 times per day. Someone above also mentioned that his modem started to work fine today. Plus, look at the forum for posts with Sync Timing Sync failures from Arris users. Bunch of them.

I'm happy to hear your modem is still up and running, @user_fd33c8. Please let us know if anything changes. 

@user_fd33c8​ Well if it's not the modem, then it's something Comcast can't figure out with their firmware for this particular modem. So either switch it out or go on and wait till they do figure it out, if ever.

@user_fd33c8​ My internet just kicked me out again after speaking with the advanced tech team at xfinity (super unhelpful) and cancelling my tech appointment as it had been up and running for over 30 hours. I hope this time was just a fluke. 

[Edited: "Language"], hope it indeed was a fluke! I got excited for a few minutes - imagine having a stable internet?!

@user_Es0824

Let's take a look at this on the back end and get another technician appointment scheduled if needed. Please send a direct message with your first and last name, as well as complete service address to "Xfinity Support". To do so, click on the chat icon located at the top right of this forums page.

 
 1. Click "Sign In" if necessary
 2. Click the "Direct Messaging" icon (upper right corner of this page)
 3. Click the "New message" (pencil and paper) icon
 4. Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list
 5. Type your message in the text area near the bottom of the window
Press Enter to send your message

@user_fd33c8​ It was not a fluke. Here we go again. shut off again just now

@user_Es0824​ ah, sorry!

@user_fd33c8​ 651000000 Hz is my downstream channel. I wonder if that has anything to do with it. That's the only real difference that I see right now. That and my upstream power levels are in the low 40s (42-43). 

@user_Es0824​ Looks like my upstream power fluctuates every other day. It was around 47 dBmV before, now around 38. But Downstream Channel was always 501000000 Hz even when I had crashes (I checked my old screen shots).

@user_Es0824​ I just noticed from your previous screen shot that your downstream power for most channels is above 8 dBmV. I was reading somewhere that it should be below 6 dBmV. Somebody suggested in other post to use Forward Path Attenuator such as this one https://www.amazon.com/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R

Edit: fixed the link

I actually have one that a tech gave to me a few days ago. I took it off after I found that it was not working at all. However that was before xfinity pushed the update. Let me attach that and see if it will work now. 

@user_Es0824​ what's the dB rating on it? Check what will the downstream power be after you attach it and restart modem

@user_fd33c8​ Our spectrum analzyer is the same. Our UDA differs though see picture below.

@user_Es0824​ Inspect all of the connectors! Please read this article https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html

I will be unscrewing and checking all the connectors inside and make sure that they are actually tight afterward.