xfinity not working


Wondering if any of the folks from Xfinity have tried activating
internet service with their own modem and without installing a mobile
phone app any time in the recent past. It doesn't work. It just
doesn't work. ->
Comcast ID Account Management ->
Sign in to Xfinity

Access Denied
You don't have permission to access "Sign in to Xfinity;
on this server.

Bill Herrin

I didn’t have a problem with it a couple of months ago, but that was when I installed Comcast Business, so likely a different user experience from residential. I had to call them on the phone to turn off my residential after the business install was completed and operational.


I had a forced modem upgrade with them earlier this year. I vaguely recall it was not without some frustration, but I managed to get it done.

I don’t seem to have a problem logging in at
Is it transient or still persisting for you?

My understanding is that the internal web page in the consumer modems is gone. App or nothing.

I don't think the options one could set from the web login are there anymore either, though I haven't bothered to confirm that myself.

Gotta love it.

The business modems still have internal web pages. Maybe they're next?

Therefore your experience is nominal.

Howdy, only responds if you're on an
unactivated cable modem connected to xfinity.

Sign in to Xfinity only works if you're not.

And neither one particularly works with Firefox. It's chrome all the way down.

I gave up and installed the app. User name, password, cable modem's
mac address. And now it's activated.

I know it's bad form to bring this sort of thing to NANOG, but come on
guys: get your act together.

Bill Herrin

With xfinity, when you plug it a "non-activated" modem, you get a
walled garden where you can connect to some of their web servers for
the purpose of linking your modem with your account. Except, as noted,
it's not presently in good working order..

And anyway, I brought my own modem which has an internal web server
and a handful of pages. Mostly status. Since it's the cable modem only
(no wifi), there aren't any user-level knobs to turn.

Bill Herrin

There are still some knobs…

e.g. bridge mode or not (usually)


I'm guessing that's only if there's a built-in wifi router. My grand
experience with cable modems counts to exactly two brands and four
models, but in each case the model without wifi was solely a bridge.
The knobs, as such, were: change the password and reboot the modem.

Bill Herrin

I thought that bridge was the DOCSIS model. Is there a choice these days? Back when I was actually working with this, the expectation is the modem was pretty dumb and not accessible to the user. It would tftp its config from the MSO and that was that.


Nope… My Surfboard 8611 has that (just Cable<->single ethernet port).

In non-bridge mode, it acts as a NAT router between the ethernet port and the single address dropped on the modem by the $CABLECO DHCP server.

In bridge mode, it passes my packets to the $CABLECO DHCP server.

Since I have business service, I’m able to use that to actually get DHCP addresses on multiple devices.

In my case, that’s a pair of MX-240s and an SRX-340.

The SRX-340 provides a backup simple network (SRX LAN ->NAT->$CABLECO) in case things go wrong with the (usually more reliable multi-homed) network. (This was quick and easy to set up and helped keep the family off my back while troubleshooting the transition to the bigger upgrades).

The MX-240s each also have a connection to Ridge Wireless and there are GRE tunnels from each via Ridge and Comcast to each of:
  + MX-240 at HE FMT2
  + VM/FRR based router at 55 South Market (San Jose)
  + Act USA in Las Vegas

BGP and traffic flow over the tunnels (BGP is loopback to loopback for FMT2 and 55 S Market, direct EBGP peering to Act USA).


Nope… My Surfboard 8611 has that (just Cable<->single ethernet port).

Cool. The models I have only bridge.

The SRX-340 provides a backup simple network (SRX LAN ->NAT->$CABLECO) in case things go wrong with the (usually more reliable multi-homed) network. (

Yeah, that's why I've been messing with Xfinity this week. I've been
stalling since I moved in last year, waiting to see how long
Centurylink fiber would work flawlessly enough that I didn't need a
second carrier. Last year I got a hold of some cable modems, made sure
I could reach the Xfinity activation service, and then I set it aside.
I figured that in a pinch I could do Internet off my phone long enough
to plug everything back in and get Xfinity up and running.

After the glitch a couple weeks ago when Centurylink sent me bursts of
other peoples' data for a day or so, I figured it was time to put a
second provider back in my mix. Imagine my surprise this week when I
went ahead and bought service, went back to the activation page, and
it didn't work.

Bill Herrin

XFINITY will send you bursts of other peoples data constantly.

That’s the nature of CMTS, it’s a broadcast network, acts like one giant ethernet.