huge internet speed fluctuations on all devices including hardwired to modem.

[Clp92]

Hello all,

For about the last two weeks we have been haveing internet speed randomly drop out to levels that are useless 1-10mbps. I have RCN 1000mbps down service and when working properly i get around 940 down. For about 9 months I have had no problems and now this problem arises. I am useing cm1200 modem connected to netgear nighthawk ax4300. this problem happens on all devices on wifi or hardwired to router and even hardwired to modem. Modem logs show errors that I am not able to understand. I have had several rcn techs on the phone and have done the usual reboot yata yata stuff. I finaly called again and they are sending a tech out tommorow moring. Hopefully he can verify that the lines are good. Anyone have any ideas? Modem logs below. 

[FURRYe38 · Accepted solution]

Remove the NG router and test with a wired PC connected to the CM modem. Do you still see these flucuations?

Most of the events are ISP related and need to be addressed by your ISP.

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://highspeed.tips/docsis-events/

[Clp92]

Sorry guys, pictures were to large to post in text.

[FURRYe38 · Accepted solution]

Remove the NG router and test with a wired PC connected to the CM modem. Do you still see these flucuations?

Most of the events are ISP related and need to be addressed by your ISP.

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://highspeed.tips/docsis-events/

[Clp92]

With router disconnected and pc wired to cm1200 fluctuations were the same. However I believe I fixed the issue. I live in an old duplex where the old owner had done the wiring. Though I didn’t know this could effect anything I took your advice and removed a splitter I found in the cable line that had been used to provide cable to a different room in the house makeing one cable with no splitters to the modem. I have not have trouble since and the errors in logs seem to have stopped . Thanks for the help. Out of curiosity what makes this cause problems? I’m assuming it changes power and adds Noise to the line? What would be the appropriate way to run cable to separate rooms in the house if splitter cause issues? Thanks again for the help.

[FURRYe38]

Yes, out of spec or no made well splitters will reduce the power and cause noise on the line. 

Glad you figured it out. 

Please mark your thread as solved so others will know. 

Enjoy.