CM1200 on Xfinity - Stalls, sometimes fast, sometimes slow - Downstream light flashing

[jboy210]

Hello,  

I have been having problems with inconsistent speeds and multi-minute stalls on my Xfinity Service for about 3 weeks.  In working with Xfinity people they said they were have issues rebooting my CM1000.  So I replaced it with a CM1200.  Now I have the same speed and stall issues and the Downstream light is flashing.   

Below are the cable connection and log screens after the logs where cleared this morning.  I appreciate any thoughts on why I am having this problem and how to proceed.

I noticed that channel 32 is blank.  Is that normal?

BTW, Xfinity rolled a truck on this issue last week.  Tech replaced ends on cables.  Issue still persists. New tech is coming tomorrow, so if anything they should check, let me know!

[jboy210 · Accepted solution]

Problem seems to have disappeared.  No more downstream light flashing, not stalls, and speeds staying between 930-950 Mbps down and 40-45 Mbps up.  Perhaps Xfinity did something upstream as the tech mentioned to increase capactiy.  Anyway everything seems to be working well.  Thanks for all the help.

[jboy210]

Attached is the event log

[plemans]

Your upstream levels are low. I've found issues when power levels are where yours are at for upstream.

your downstream levels are high but not crazy high. Just slightly out of optimum spec. 

Any splitters, amplifiers, or attenuators in line? 

with 2 modems having the same issue, I'd be looking at the line again. 

[jboy210]

Thanks for the info.  The Xfinity tech was here this morning.  He checked the lines again and added a splitter with attenuator which appears to have pulled the downstream power down and upstream power up.   See the attached results and please comment.

After he did that the speed was very slow for awhile (50-200 Mbps on Xfinity's speed test) even at 9AM on Saturday.  But by early afternoon it has climbed up to near expected, 900+ Mbps. However, I still see the downstream light flashing occasionally. 

I will monitor the network to see if this fix is permanenet.  I am especially interested to see what happens Monday.  He did mention with so many kids and workers on Zoom for school and work, they are having to revise (he used the term split) much of their cable plant.

[plemans]

The problem with attenuators is they don't "boost" the upstream. They basically add resistance to the line so the when the modem communicates back with the cmts it senses a reduced signal so has to increase its power to talk to it. It might help, it might not. 

[jboy210]

So what is the proper repair to get the numbers back in line?  Does a change need to be made at the head end?

[plemans]

It'd still be a line issue.

Like I said, the attenuator might help. Try it. If your speeds are staying stable, I wouldnt' worry about it. 

If they continue to drop, then a different technician needs to check/fix the line. 

[jboy210 · Accepted solution]

Problem seems to have disappeared.  No more downstream light flashing, not stalls, and speeds staying between 930-950 Mbps down and 40-45 Mbps up.  Perhaps Xfinity did something upstream as the tech mentioned to increase capactiy.  Anyway everything seems to be working well.  Thanks for all the help.

[plemans]

glad to hear it!