Saturday, February 25, 2017

Things I learned connecting my upgraded Comcast modem (Arris TG1682G)

Comcast sent me an email offering a modem upgrade that would enable higher speeds. I figured I’d have to do it sooner or later so I accepted the offer. Higher speeds would fit with Comcast’s “pay to play” network non-neutrality strategy [1].

I got things working, but it was a bit of a cluster. Comcast tried to make this self-serve, but they didn’t quite hit the mark.

I’ll skip the boring details of things that didn’t work and chat advice that was misguided and just list the useful bits I wish I’d known:

  1. I replaced a simple, compact wall mounted ARRIS CM820A/CT (no wifi, coax in, ethernet out) with a much larger standing ARRIS TG1682G (download manual from link. Has 4 ethernet, VOIP phone, wifi, xfinity hotspot).
  2. You can disable the WiFi and the xfinity hot spot and you can run it as bridge or router. See below.
  3. XFINITY support can remotely configure changes, but they can take hours to be implemented. I’m guessing there’s some sort of slow queue.
  4. The TG1682G ships with two high quality coax connector cables. My original Comcast installer had trouble with excessive signal strength on the original device and installed an inline damper (resistor?). I reused that cable.
  5. You have to activate it before you use it. Even after all lights are green and it seems to be on the Net it’s really not. It’s locked out by Comcast until you connect to the device (wifi or ethernet) and navigate to (if that fails, try You should see an activation prompt. The ’text code’ method didn’t work (message arrived much later) and the login method failed too. I entered my account number and address. You have to accept a new web services agreement. I don’t want to know what I agreed to. 
  6. Once it’s activated go to to configure the device using credentials of un=admin and pw=password (yes, “password”). You will be prompted to change your password. I suspect 99% of users don’t because the standard setup skips this step.
  7. From the web interface you can disable wifi (I do wifi via Airport Extreme), adjust firewall, and go to bridge mode. For now I let it in router mode (so I have two firewalls - Airport Extreme and Arris). I don’t use P2P so I upped the firewall to standard security
  8. To disable the XFINITY “hotspot” service (used to provide roaming wifi services to their customers) you can use the xfinity app on your iPhone or go to
I pay $80/month for Performance 25 Internet with Blast Pro; allegedly 200 down and 10 up. To test I connected by Gb ethernet directly to the router and gave me 238 down and 12 up. Which is what I pay for, but not faster. Maybe the higher speeds are coming?
- fn -
[1] Shortly after the start of Crisis-T Comcast capped our network capacity at 1TB/month. The timing might have been coincidence, but maybe they were waiting for the end of net neutrality.  Carriers do bandwidth caps so they can extort funds from media partners (ex: Netflix) who pay to be excluded from the cap. Higher speeds make economics sense then, because they enable more media consumption.
Update 3/12/2017
A few weeks after I’d installed the Arris a comcast technician came by my home with a new inline filter. According to this gentleman the new Arris modems chat with each other and this was somehow unwanted.
Knowing Comcast this all sounds ominous. On the other hand, I don’t see how a dumb filter would block a typical digital signal even over analog cable wiring.
After installing this additional filter I had no net service. I had to power cycle the modem and wait about twenty minutes to restore service.

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