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DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

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Re: DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

Frequent Visitor

Re: DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

Turns out that while I bought the modem on ebay, Comcast had it in their database as being one of their own modems.  And therefore wanted to charge me a $10/month leasing fee to use it.  Which negated the benefit of me buying it off ebay.  So I ended up returning it.

 

Never did solve the original problem.  I suspect what was happening is that Comcast's systems were commandeering my modem thinking it was one of their own.

Frequent Visitor

Re: DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

I'm hoping that by enabling and then disabling the public wifi via https://customer.xfinity.com/#/settings/security/hotspot that that will help me slay this issue.  Somebody on a reddit thread seemed to have success with that.

 

It took me 36 hours before I finally saw the SSIDs (xfinitywifi) and now it looks like it will take another 36 hours before it's disabled.  So just documenting what I'm seeing for the moment: it created two SSIDs (xfinitywifi), using the same MAC address prefix as for my private SSIDs.  It used one of the what I'm calling a floating suffix: C1.  And it seemed to create a new suffix to use: BA.

 

 

Frequent Visitor

Re: DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

Things are getting stranger. I noticed the following:

  • the 2.4Ghz MAC address ends with B8.
  • the 5Ghz MAC address has the same prefix and ends with C0.
  1. The modem isn't emitting on those two MACs when I have them disabled.  Rather it's emitting on parallel MACs: same prefix, but different two digit suffixes, e.g. BB, BD, B9, C1 and C2.
  2. And when I have the wifi enabled for the two "primary" MACs, those two MACs finally show up on my Wifi analyzer with SSIDs. But the other ones don't all go away: I still see emission on BB and BD for instance.
  3. In contrast, when I cycle through enabling the wifi and disabling it again, such that modem is operating the way I want it to operate (for all of 5 minutes), I get no readings for that prefix at all.
  4. And I get no readings at all on that prefix when I turn the modem off.

As I scan through other MAC addresses that I can see (I'm in a condo rental), I notice that the same thing seems to be happending for other MAC addresses being used in the apartments surrounding me.  The primary MAC addresses which have SSIDs are also emitting on MACs with the same prefix (but different suffixes) and without SSIDs.

  • I'm willing to bet these are all Comcast modems (and likely the same modem I'm using, except leased from Comcast while I own mine).   So it looks to me like this modem or similar modems from Comcast are filling up the airwaves throughout the building with emission without SSIDs. 
Frequent Visitor

Re: DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

Edit: Well I thought I had it conquered, but I don't.  I just flipped it from bridged mode to not-bridge mode and manually disabled the wifi again and at first it seemed to have worked: I wasn't seeing anything emitting via my wifi analyzer app. And the corresponding LEDs weren't blinking either.  But after about say 5 mins, it started acting up again.

Frequent Visitor

DPC3941T wifi turned off, but still emitting in 2.4 and 5 Ghz

Hi,

I have the DPC3941T modem, and I found that it's still emitting on both 2.4 Ghz and 5 Ghz bands even though I have wifi turned off.  This is true for when I have the modem operating in bridged mode.  And it is also true for when I have bridge mode disabled with wifi specifically disabled.

 

When I use the admin console for the modem, it shows the mac addresses for the 2.4 Ghz and 5 Ghz as being greyed out.  But when I use a wifi analyzer on my android cell phone, I can see spectrum being emitted on both mac addresses.  The other strange thing is that it's periodic: it turns on (to 40dbm) on a specific channel.  And then goes away.  And then comes back on again. And there's no SSID.

 

I noticed too that the LEDs for 2.4 and 5 Ghz wifi are respectively blinking as well.  This is what actually prompted me to dive further to see what was going on.

 

So question, is there a way to disable this through some back door I'm not seeing on the admin page for the modem?  Or does Comcast have a back door for disabling this?

 

Edit: I should note, this is not leased from Comcast.  After leasing one of these from Comcast, I went ahead and bought one of my own off ebay.

 

Thanks!