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user_ab2oer
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Tuesday, July 22nd, 2025

Lag and dropped packets

Hi,

Several times each day there is a short period of time, usually about 5 minutes or so, when I experience lag times of 2-5 seconds and dropped packets getting to the Internet. I have monitored the connection using ORB and I have screenshots of this activity. I am using a Motorola SB6120 DOCSIS 3.0 cable modem hardwired to an ASUS AC-1750 router. Whenever this occurs the delay is always between the Router and the Internet. Any advice about how to figure this out would be appreciated. Here is an example:

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20 days ago

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XfinityAmandaB

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1 month ago

 

user_ab2oer Thank you so much for stopping in for help with this connection drop you are encountering. That would be frustrating to deal with even for a short time, so thank you for letting us know. First, with the information you provided, I would start with the modem you are using currently. The SB6120 is not currently one of our supported 3rd party devices. That, of course, can cause some issues. If you check out our Device info page, you can see a detailed list of what 3rd party modems we currently support.

 

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user_ab2oer

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Thanks for the reply. I will look into upgrading my cable modem. However I don't understand why that would make a difference for random lag and dropped packets since I only have 136/40 MBS service and those speeds are well within the specifications of the SB6120.

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30 days ago

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XfinityRaf

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When you see this packet loss & lag, are you streaming or gaming? Is it during a certain time of day? 

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30 days ago

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user_ab2oer

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No gaming here. It occurs at random times of day. Usually notice when browsing, web pages take 2-5 seconds to load. 

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30 days ago

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XfinityAmandaB

Official Employee

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2.5K Messages

You can check more on your signal details to see if anything is off when you do run into the issue again. Check out our [internet troubleshooting checklist](https://www.reddit.com/r/Comcast_Xfinity/wiki/knowledgebase/troubleshooting/internet-checklist/). If you look over the section "4. Have you checked your modem's RF signal levels while the issue is occurring?", it will show you what you should be receiving and where to check. Feel free to share your results here, just be sure to remove any personal information like IP addresses or MAC information.

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

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30 days ago

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user_ab2oer

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Thanks, good idea to check the RF signal to the cable modem when this is occurring. I will do this and report back. 

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29 days ago

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user_ab2oer

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22 days ago

I have resolved this issue as far as I can tell. I changed the ethernet cable from the modem to the router. I had used the same cable forever but it appeared one of the connectors wasn't fully snapping into the port socket so just to make sure I changed the cable. I also viewed the incoming cable signal and it was showing levels between 17-18 dBmv which is above the cable modem spec and above what Xfinity recommends (-7 to +7 dBmv). I added an 8 dB attenuator to reduce the input signal to about 9 to 10 dBmv so it is now within spec for the cable modem. Between these two items the random 2-5 second losses of connection have been eliminated. My current service is 150/40 so just to make sure I am getting all the speed the service offers I ordered a new DOCSIS 3.1 32x8 modem which is overkill but I will see if I now get a little better speed and perhaps less lag delays over time. Thanks for your help!

(edited)

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XfinityMatthew

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702 Messages

@user_ab2oer  We are certainly happy to hear that everything seems to be working well now. We appreciate you taking the due diligence to go so in depth and get the issue figured out. If you notice any further issues and want us to take a look on our end just let us know and we'd be happy to take a look at things. 

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Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
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20 days ago

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