Any cable modem experts out here?

I have a problem with a network that frequently loses internet connection. The LAN network is 100% OK (Ubiquity Pro USG + 24 Port POE switch etc. I spend a lot of time trying to find out why the internet connection clunks out during heavy traffic. For example, during the morning Peleton virtual bike race and late-night x-box gaming…

Recently I had a less severe situation solved by the cable technician who determined that the signal strength was too high, and after he installed an attenuator, the problems disappeared.

The problem is that this customer is an Xfinity residential customer for whom its hard to get intelligent tech support other than resetting the modem and power cycling it…

The modem is Docis 3.1 compliant, and the contract is for Gigabit speed.

I am a ham radio operator, and when I compare the values obtained from the Modem to the information I found online, I have a hard time interpreting the differences if any.

We are hoping that there is someone around here who can have a look at these results and let me know if the signals are within specifications and what corrections to make if we are not.


I would recommend you also ask this question in the Mac Geek Gab forums.

This is the kind of problem Dave and John live for.

(or email the question to

1 Like

Thanks, I will create an account later today.
I also asked the question on DSL reports and Small Net Builders.

You mention you think it’s a modem issue but then you talk about attenuation which would be wireless lan.

Are you sure you know where the problem lies?

Have you checked your WiFi channels with a site survey?

Yes I did and it also happens on the wired (Ethernet) connections.

And yes signal strength also applies to the RF signals transmitted via the coax cable…

Is this a customer owned modem or is it leased by the cable company? I have solved so many issues by buying and provisioning my own modems over the years (not to mention saving $ on monthly fees). That might be worth looking into.

Whenever possible I encourage clients to buy their own modem. Not only does it save money but more importantly its a plain modem and we can manage the network ourselves.
Getting they standard cable boxes in to bridge mode is not always easy or even possible (cox doesn’t want to do this). And creating a DMZ isn’t a great solution either.

It’s been a while since I dug into cable modem stats,
but signal strength should be above 37? and all your
numbers are there. The key thing is the number of
corrected and uncorrecteds, If it’s a cable modem
issue those numbers are in hundreds and thousands.
Don’t think cable modem is the problem

You mention Ubiquiti, have you checked your Fast
Roaming wireless settings? Also, if you are using
static IP? Set the reservation in the controller rather
then on the device.

(Will assume Ubiquiti firmware and controller are at
latest level)


Yea I have checked the LAN side. Its not WiFi related it also happens with wired devcies

Have you checked controller DHCP timeouts?

(I had similar issue and nailed IP out
of DHCP range via MAC reservation)