Xfinity XB3 hardware mod: Disable WiFi and save 2 watts
43 comments
·March 30, 2025wpm
nkrisc
> If some dumb bozo wants to get the ISP deluxe package of gateway/router/DNS sniffer/shit-tier WiFi AP all rolled into one box, fine.
Recognize that nearly everybody is a “dumb bozo”. Most people do not want to manage a home network.
wpm
Providing my own hardware does not equal "manage my own network".
It usually does mean "my network works better".
ascagnel_
Even people that know how to manage a network may not want to manage their home network.
jchw
The normal Comcast plans do let you do that, this is some weird special plan. You can hook up a standard DOCSIS modem and then DHCP lease an IP.
There are a lot of technically-proficient people who refuse to do this anymore. I guess it is a non-zero amount of work, but it really, really isn't that much. The direction we're headed in is pretty obvious: some day, sooner rather than later, the era of customers being able to use their own cable modems for DOCSIS internet will slowly end, as the people who bother become more and more in the minority.
iforgotpassword
This was the norm in Germany for a while. Then we got a law ("Routerfreiheit") that forces ISPs to allow you to use and modem/router you want. Before that you couldn't do it with DOCSIS, but it kinda worked with DSL, if you could somehow get the PPPoE credentials.
Nowadays they have to provide PPPoE and voip credentials, and cable providers need to provide a service where you give them the Mac of your own modem and then it gets tied to your contract.
barnas2
Cox also lets you do this, although they'll straight up lie to you on the phone. The rep very confidently told me I could not use my own equipment, and was required to use theirs, despite their website claiming otherwise.
ryandrake
The customer support reps might just be poorly trained (yet confident), and not lying. Calling it "lying" requires there to be an intent to deceive.
lloeki
In France there's a long (as evidenced by the phpbb forum) active community of people doing that, the keyword is "box† bypass"
https://lafibre.info/routeurs/ (see "remplacer XXX par un routeur")
It's somewhat easy if you know network stuff (DNS, DHCP options, CIDR, routing, prefix delegation, etc...); if you somewhat know about those and can navigate some docs the hardest part is figuring out what the ISP expects in terms of magic bits so that it decides to:
a) hand you out v4 address (DHCP) / v6 prefix (RS)
b) allow routing (notably for v6 prefix, sometimes /64 may work OOTB but getting the /48 or /52 you're supposed to have doesn't route without proper RS DHCPv6 options)
c) unlock throttling (some throttle packets unless magic bits are sent in a specific way)
Well; that, and having the proper hardware (e.g obtaining an off-the-shelf 10-GPON SPF module compatible with what your ISP provides might range from very pricey to unobtainium). I'm lucky because my ISP chose a split ONT/router strategy and I just have to plug my own router in the GPON ONT over Ethernet.
† an ISP-provided router is just called a "box" - from "set-top box" - commercial names being "box" concatenated with the ISP initial or name: Bbox, freebox, livebox, neufbox/box SFR
reddalo
It's even better in Italy. There's a law called Modem Libero (Free Modem) [1], thanks to that every ISP must give you all the connection parameters (for free) so you can install your own modem.
P.S. thanks, now I know why Iliad (Free in Italy is called Iliad) names their router "Iliadbox" :) that naming is not common in Italy
[1] https://www.dday.it/redazione/51863/modem-libero-e-ftth-tutt...
sschueller
That is why I stick with my ISP[1] even tough they are a bit more expensive (CHF 64.75 per month is still very cheap) than others. I have an OTO (Optical Termination Outlet) port with 25gbits in both directions and nothing else. No GNAT and no other bullshit.
They have a "nerdmode" switch on their website.
dmos62
What bandwidth are you allowed? I presume it's not 25 gbps. For reference, I pay 15 EUR for something like 500 mbps.
sschueller
Their Terms of Use specify:
> Fair Use Policy The Internet subscriptions for private customers are intended for normal personal use. Init7 reserves the right to temporarily or permanently restrict or discontinue the provision of services for connections whose data volume exceeds 0.5 petabyte (500 terabytes) in a period of 4 weeks, or to take another suitable measure.
So that would be full blast for over 40 hours...
mschuster91
The answer to this is government regulation. Here in Germany, ever since 2016 we have the "Routerfreiheit" codified in law [1] - despite numerous attempts from wannabe crap-peddlers and cheapskates over the years, it still stands strong. Just this year, it was confirmed again, that the freedom to choose your router even applies to GPON [2].
ISPs here are required by law to state the technological standards they use, and consumers can request the required authentication data (for DSL PPPoE) or, in the case of hardware-based authentication with MAC addresses (for DOCSIS), submit these to the provider.
In practice most will rent from their ISP, but the competition is so strong that cheap crap routers are rare, usually ISPs make a point in advertising customers will get an AVM FritzBox - the ultimate market leader for good reasons.
[1] https://www.bmwk.de/Redaktion/DE/Artikel/Digitale-Welt/freie...
[2] https://www.teltarif.de/bnetza-glasfaser-routerfreiheit-netz...
easton
I’d note that (outside of Comcast possibly being mad at you breaking the modem), sometimes they push a bad update and you need to reset the modem, and last time I did that I needed to step through the initial setup on the WiFi network before activating bridge mode. So if the wifi hardware is broken you might need to jump through hoops to get through that setup (or swap the modem).
p1mrx
I tried a factory reset, and was able to configure bridge mode via ethernet.
don-code
While I doubt they'd find it - the SOP for issues with these modems must just be to replace them with a new one - something tells me Comcast wouldn't look kindly on physically modifying rental equipment.
p1mrx
I'm not sure how NOW handles replacements, but the modem has a label saying "This is customer owned equipment and should not be collected or swapped by Comcast personnel, unless within warranty repair."
The FAQ says "your NOW Internet Gateway comes with a 90-day warranty" so perhaps they'd care somewhat about mods within the first 90 days.
johnklos
It amazes me that devices with Intel Puma chipsets are still sold new and are still in use in 2025. That's another story, though.
The number of wifi networks that're running around us has gotten so crazy that it's no wonder we all need wifi-6 to even get reasonable speeds. I'm the kind of person who goes around and disables wifi absolutely everywhere possible, so this is good to know, but what'd be even better is if devices stopped running wifi networks behind our backs. Sigh.
technofiend
You really want 6e or 7 these days so you can shift to 6GHz. There are many more channels available, adoption is limited so there's less congestion and the signal attenuates more quickly and has higher free-space path loss as well. Sounds like you may already know all that but for anyone thinking about investing in an upgrade, the reasons listed above are why you'd want to invest in the latest tech.
sightbroke
Why would faster signal attenuation be a good thing?
diamondlovesyou
Less area means less sources of interference for others (this property is also true in the other direction). So the attenuation reduces the signal area, and stronger attenuation lets the transmitter be "strong" in the house without the downsides in congested areas.
Cerium
Don't need to fight for spectrum with the neighbors.
pmontra
Small houses don't need a signal that travel through many walls. Probably no roof and floor too. So you can trade speed for range and have no overlaps with neighbors.
Instead large houses need signals that go through roofs, floors and walls. But they probably also have a lot of family members inside, each one with their one, two or three wifi devices that interfere with the rest of the family. Maybe one repeater per room and 5 or 6 GHz would be good there too. 3 different video streams to people of the same couch could still be challenging.
heavyset_go
Imagine sharing the spectrum in an apartment in a high population density city.
mrheosuper
notice wifi standard does not guarantee which frequency it will use. You can have wifi 6 on 2.4ghz wifi
ThatPlayer
That does depend on which wifi standard. Wifi 5 is only 5ghz, wifi 6E is only 6ghz, and there is no wifi 6 on 6ghz. 6 being separate from 6E.
Check out the table on wikipedia: https://en.wikipedia.org/wiki/Template:Wi-Fi_generations
gorbypark
Yeah, I've been playing around with the "new-ish" ESP32-C6 chip. It's a $6 dev board, so probably in the sub dollar range in bulk for the chip itself, and has WiFi 6! I originally thought WiFi 6 meant 6ghz, but it's limited to 2.4ghz.
6SixTy
The XB3 hardware isn't new. I was given one circa 2017 and now knowing that they used Intel Puma makes so much sense now.
quailfarmer
Yes, this is great! They gave me a similar model under the same deal, and it had a fan that would ramp up and down all day and night.
rasz
In 2014 Liberty Global decided to offer UPC Wifi Free - free roaming wifi on all cable modems they manage. Your own modem would advertise HotSpot and share your own cable connection. In theory you could opt out, in practice when I tried it just meant removing my login credentials while my box still shared and disabling Wifi locally would bring it back after a while. Thankfully Cisco EPC3925 uses BCM43225 mpcie Wifi card and unplugging it removes all mentions of wireless functionality from Setup, problem solved.
technofiend
This is exactly what Comcast does with their Xfinity service if you use one of their devices.
heavyset_go
It's something you can disable with a toggle.
metaphor
Uhhh, sanity check: If you lived in a state like Hawaii where the cost of residential electricity approaches outrageous territory (i.e. ~$0.50/kWh), then you'd be hard pressed to save $1 per month trimming -2.4W nominal consumption with this hack.
Perhaps I'm just naive, but this struck me as the buried lede:
> ...but even in bridge mode, the gateway broadcasts several hidden SSIDs with no option to disable the radios.
pastage
10W idle for edge appliances is crazy when you think about it.
On a yearly basis if you lower consumption by one watt it saves you 8.5kWh My network and internet access needs between 1-15W, I save about 80kWh compared to this setup. Even with one watt less it actually makes sense if you care about many installs.
My rate goes to infinity at the darker times of the year.
p1mrx
The cheaper service more than offsets the cost of electricity, I just prefer to use an OpenWrt router, and it bothered me to burn more energy on a worse modem that spews WiFi for no apparent reason. If xfinitywifi were on the list, I would at least understand what it's for.
maccard
There’s 13 million households in California. Theoretically, if every household saved 2 watts with this change it would remove a small gas power plant from the grid. It’s nothing for one household but this sort of efficiency at scale makes a difference.
metaphor
That's all motherhood and apple pie, but it's a red herring with no basis in pragmatic reality (i.e. not how the calculus of utility-scale power generation industrial planning/ops works), and wholesale disingenuous to posit that even a residual percentage of those households---say, asymptotic to the proportional marketshare of Firefox users in the state as a comparatively low friction proxy aspirational target---would even attempt this hack...to say nothing of its trade-offs or implied liabilities to the end user iff successfully implemented...or how Comcast would be incentivized if adoption achieved a critical mass that made the hack observable (either technically or monetarily) on their end.
Not to discredit the author for sharing the insight, but the hard sell of saving 2W consumption simply isn't a prime mover here. If anything, mitigation of implicit side channel RF interference when the hack is paired with a OpenWrt router (as the author apparently intended) makes a lot more compelling sense...but now we're talking about bootstrapping an additional appliance into the setup, rendering contextual discussion of power savings objectively moot.
the_svd_doctor
In SF Bay Area my PG&E rate is also close to 0.5$/kWh…
metaphor
My condolences...looks[1] painful.
[1] https://www.pge.com/assets/pge/docs/account/rate-plans/resid...
Every ISP should be required upon request to provide the necessary hardware to provide a single IP address on a single copper cable. If some dumb bozo wants to get the ISP deluxe package of gateway/router/DNS sniffer/shit-tier WiFi AP all rolled into one box, fine. The opt out should be as simple as “I have my own equipment, I understand that any support call with you will stop after a public IP is found to be working on premise, now get the hell out of my way thank you”