When can I JUST use TM internet modem as ONLY a modem, in BRIDGE mode, with NO NAT, NO firewall, and frankly NO Wifi.

OK -- Sounds good, but let me ask to confirm a few things:

-- I'm assuming then that your mesh router is providing the DHCP so that is the device that is handing out the IP's?  This is critical, since it was at least reported that the DHCP was limited to 20 dynamic IP's internally.  I assume then also, you are at least ignoring their WiFi and using only yours.

-- Someone else mentioned that it did NOT support IPv6 properly. Going forward this will be more of an issue than it is today.

-- Double NAT -- There are a few people I’ve heard that had significant issues, since this caused some services to be rerouted

-- Static IP's and port forwarding -- There are many reasons and situations where this is critical.  For instance, I've got some very old devices that I need to reach on demand, some from outside my network, on the internet.  If I can't predetermine the IP's for these devices, AND specify which ports and traffic is routed to them, then these devices will not work, or will be randomly unavailable.

-- Bridge Mode -- The reports that I heard that originally caused me to ask / report these issues, is that they said it would NOT support bridge mode.  This means that their device must first be configured, and then if you are "lucky" or brilliant, you can force your router to UN-do the TM router, and then apply it's own settings.   

-- How do you overcome the requirement for bridge mode?  I know in the past with several home WiFi routers that wanted to add their own NAT, DNS, and DHCP, if you didn't disable DHCP, DNS and enforce bridge mode, you just couldn't get your devices working properly, nor could you get these devices all on the same subnet.

Each problem I mentioned above have caused a lot of work to overcome at some point, which is why once you get everything set up, you really do not want to make any changes to your network.  Some problems are just virtually impossible to easily overcome.  Even today, I've got an old "WiFi CELL SPOT" with T-Mobile firmware.  It's a fine WiFi as long as I only use bridge mode, do not use their firewall, NAT, DNS, DHCP etc.  But, that firmware will NEVER EVER be updated by T-Mobile and the hardware vendor, NetGear.  But then, since they support BRIDGE mode, there's no problem, either.

REALLY, let me know, or someone else can report these issues.  The only reason I'm writing this is that I WANT to see this working easily and reliably.    

Bridge mode, double NAT and all the rest has been talked about her ad nauseum. We all know it sucks and T-Mobile is fully aware of our frustration. Just about every week a new user comes here to complain. The can is dumbed-down for sure. Designed for the non-technical plug and play.

For me it's an irritant but not worth staying with Spectrum. Not even close. Their constant price increases are offensive. Would never consider going back to that company. 

For $50 a month I get great speed, better than Spectrum was and reliable service. I'm in Dallas so I'm sure that helps. I've found workarounds for the port forwarding and the rest. Hopefully these limitations are temporary.

Agree that is the perfect solution if all you are using internet for is a very limited number and type of device, and need zero configurations to enable other services.  For instance, my mother's setup is ONE WiFi connection to ONE computer, unless I'm visiting.  If that's the market TM is after, then fine.  But cord cutters are likely going to be connecting 20-30 devices, and then add thermostats for my AC and heat, all the new cameras, doorbells, garage door openers, sprinklers, my plumbing connections, and eventually toasters and my refrigerator.  Does TM really expect to make these types of customers happy??  Good luck with that, but it is NOT going to go well for TM if they try.

But, my point was that it is MORE difficult to provide settings, setup and especially tech support than it is to SIMPLY ENABLE PASS-THROUGH with a minimum of services and settings.  That way, there's a clear line of responsibility from them to me.  More importantly, TM can provide 100% of what I need at extremely low cost, and high reliability.

If they are going to maintain all the settings of my network, then they will very often need to send a networking expert out, since I generally have at least one device that isn't working properly.  Then sometimes the problem is setup, firmware on the device OR the WiFi, or physical cable, or sometimes it is my router setup.  Someone that has that capability to straighten out all my networking problems is going to cost TM at least $50 PER call, and most often, it will NOT be their problem.  In short, they'd be crazy to even want to try to provide that level of service.  NO internet provider that I know of today, provides that kind of service.

I've never had any need to even try to log into my Spectrum Modem.  Why would I ever need to??  regardless of what the problem is, assuming it is getting 115 VAC, a tech MUST come out to do the repairs to either the cable or a modem replacement.  The ONLY thing Spectrum ever has to do, is to read the logs, which tell them how many times it rebooted, what the signal level and bandwidth is now, and the history.  They can also see if it has DNS, DHCP to the first device, and even if it is connected properly to my hardware.  Then, they might send a tech out.  Most often they replace connectors on the cables, inside or outside my house, or sometimes the cable modem itself.  But, ALL of that troubleshooting is INSIDE the modem.  My only involvement might be to reboot it via power down, and to make sure it is still getting power.   If there's ANY OTHER network problem, it is MY SOLE responsibility and labor.

464XLAT/CGNAT topology breaks all the use cases people are citing when asking for this change.

This approach, by design, is not there to provide typical dual stack functionality.  It basically cannot do it without specific care taken for additional translation/preservation of details needed to provide the desired NAT functionality.

Makes bridge mode/port forward options irrelevant  because it breaks everything in higher layers.

Even the older Askey LTE only model that provides most every typical router functionality (sans bridge mode) cannot resolve the issues.  Not even the DMZ option would resolve things properly.

Unsolicited inbound traffic is filtered/blocked at a higher layer, so packets never even make it to the modem in the first place.

Search on the terms bridge mode or port forward.  You will get a LOT of hits dating back a year or longer about this problem.

There have been hints/rumors/hearsay that changes to their stack MAY eventually come that could resolve issues, but nothing has been officially stated.

Until such time, about the only thing people can do is pay extra for third party workarounds, like perhaps a VPN service that supports P2P properly enough to allow you to assign specific ports to forward through that VPN.

I've done the research now, and have concluded that this is definitely not ready for prime time.  Not only that, but I've concluded that TM is sadly only going to cater to low end users.  IF TM is going to go after networking and the ISP market, then it will fail unless it is also fully supports the "business office environment".  Where is that located today??  Most employees' offices are no longer in an office building.  Call their office, and you'll find that it is really located in their home, and not down a long hallway.

Call most business's main office number, and instead of a PBX, you will most often reach that person's cell phone-- their PERSONAL cell phone.  Businesses are moving most all their workers to work offsite, and much of that "branch office", is really at the employee's home. or where ever they happen to be at that time.  So, if our cell phones are now acting in the role of the extension at my office, it is ALSO my business phone. 

What about the "company LAN" or our shared apps, shared data, and security?  That too is being replaced in teh cloud so it will increasingly not matter, where the physical office is located.  Google WorkSpace which we use as a small company, is also now scaled up to handle thousands of employees.  So, now our "company network" is not behind a firewall as it was years ago.  The engineers at Google really do know what they are doing for enterprise customers.  We had to migrate our "network instance" to a large company, and that only took our IT staffs an hour, with Google's help to implement the transfer.

Recently, I had to work with troubleshooting significant problems with a 5 year old ARRIS cable modem, remotely from 100 miles away.  THIS IS a "consumer product", and I'm going to reverse my stance and say that most all vendors that are providing services for consumers and companies ARE providing FULLY ALL the features for both styles of customers.  It's the only strategy that makes sense.  And, instead of less capabilities, there are significantly more options and capabilities in all the new modems.  They are all ready and capable, and designed specifically so the identical hardware can front end a $20,000 Cisco router, or my XBox and Roku.  And in today's market, TM is planning on eliminating "business use"??  Most homes ARE GOING to be all types -- SOHO, SMB and enterprise offices, as well as homes.  Those that are not, will become fewer and fewer.  

Even though this ARRIS device I was troubleshooting appeared to be defective, from the consumer's side I was able to use their PC to configure more than most commercial routers, and this was as it designed over five years ago.  Likewise, many of the detailed logs are available to the users and even more detailed logs and configurations are available to Spectrum, remotely.  I found their support engineers, and we could both work on that device together, remotely.  We both could see that in the past week, this was going on and offline about every two minutes.  We also determined that the problem was likely the wiring, and not the modem.  No guessing in the dark, the on-site techs had to rewire a fair amount of connectors, both inside and outside the house.  Then, perfect internet

At this point, I really can't justify wasting my time redoing things another way, just because TM is too stubborn to provide a device that could be used in business OR home use.  You can always hide features, but you sure can't add them if they don't exist.   ADD PASS THROUGH and BRIDGE MODE!

I have a number of calls from the "business reps" at TM.  Here's some of the things I will report:  When providing a new service or new hardware, you are choosing to not only cripple the devices as you've done with the modem, but you've also chosen to not even allow pass-through to work.  That means that your new devices and services are specifically designed so that they can't possibly work in a business environment.  Even your old obsolete "Cell Spot Wifi Router" designed by NetGear, had bridge mode where I could use it as a pass through, or as a Wifi dumb target within a LAN, (which I am still doing today).  You can easily add a UI "dumb mode" for users that might cause more service config problems, and that will keep it simple for them, while providing an advanced mode for regular users. 

I'd also talk to them about TM's DIGITS initiative.  It too, seems like it had a great start to provide a means for a SOHO business with a cloud based Mini-PBX.  Instead, it appears the product was abandoned… Not only is there no further development, even what they did release, cannot be used.  The Android app hasn't had an update in years--That said, the app actually stays logged in and mostly works, although synchronization between the app and the phones doesn't work reliably.  PC's --- Both the installed DIGITS app, and the web based version of Digits is a joke.  Both log out after 20 minutes, and can only be logged back in with a new text message code, sent to your regular cell phone.  Whoops…  To me, these are rather glaring problems that won't ever be solved and brought up to business standards.  

I was really bullish on TM providing inexpensive ISP services.  but someone that is a strategist must get involved or TM will fail, and us users with them.  I'll have to stay with Spectrum for now, even if it costs more $$.  Overall with my time, it is a much better and less costly.

I have my T mobile gateway connected to my existing network with a Cat5 cable.  Works fine, current network provides all services, gateway just connects to tower.  T mobile internet app provides monitoring and settings.  Hope this helps.

Sometimes I'm sorry I brought up a specific point or question.  "NAT" as I knew and defined it is obviously implemented simply, but only in simple implementations.  I searched for the terms, "XLAT/CGNAT" that you used, and learned I didn't have a clue what's going on in designing carrier level internet services.

First, I found an “old” 2016 Cisco article that clued me in on how little I knew:

https://www.cisco.com/c/en/us/td/docs/routers/crs/software/crs_r4-3/cg_nat/configuration/guide/cgnat_cg43crs/cgc43cgn.html

It turns out, TMO, starting from scratch is solving several problems that now face all providers.  One of them is the dearth and cost of carrier IP ranges.  According to this article, everyone eventually will be using these types of technology.  So, NAT as I knew it will no longer exist.  Similarly, although I love my hard drive based DVR since the days of Replay TV, it is a dead technology that will quickly be eliminated.  [At least I resisted long enough that skipping commercials while streaming became a real issue that had to be solved, or endured, rather than ignored.

The issue I guess I need to resolve is not the specific implementation TMO has today.  The criteria for how great will be determined simply by how committed TMO is to winning this market, and do they have the technical excellence to solve whatever issues arise while they get there.  Sure, it will have rough patches, but if they are committed, they will win.  If not, someone else will.

Picking the right company and technology is not a trivial exercise, and the stakes for a consumer are sometimes huge.  Legere's office himself saved my butt years ago before he was at TMO.  He was around when ATT came up with the brilliant idea of merging landline divisions with a cell company.  The result??  My first bill went from $60 to $1,200 in one month, and they only saw I hadn't paid.  No proof that I didn't owe, and had paid any bills could convince them to keep my cell phone on.  Why??  the merger forbid one company from accessing ANY of the billing records from the other.  So, when some moron merged the databases, some companies that owed millions, only had to pay my $60 bill.  IOW, it was so screwed up, no one could sort it out.  Legere's office saw it all, and at least would overrule the turn off orders immediately.  After a year, I got a full refund for the year.  I suspect experiences of stupidity like that is why and how he shook up not just TMO, but the whole cell industry.  In short, I bet big on him and his management about 15 years ago, and I'm happy to say it was the best decision I could have made.  I will be interested to see if TMO can fix and control everyone from Sprint, or horrible practices of Sprint will win, and ruin both companies.

Thanks for your detailed analysis, and it sounds to me like ALL next gen modems, including from the cable companies, must have the type of control built into them to build out a carrier based internet provider.  IOW, these design decisions are not accidentally created problems.  They are simply artifacts of the newer technology that we must all adapt to in the future, and eventually, it will work extremely well. 

Isn't TMO the only company that implemented using all the existing Wifi bandwidth for phone service??  THAT was revolutionary, and innovative solution that had huge benefits from both a technical and a business perspective.  Other companies either didn't follow, or did so slowly. 

Not having Bridge Mode is a PITA for me.  I need control over the DHCP to set the subnet and fixed IP's.  The old ASK gateway provides this.

Early on the ASK's had a problem with IPv6 over WiFi.  After a half-year of T-Mobile Engineering saying there was nothing wrong with it, they finally admitted it and fixed it.  But for a while I tried a Nokia.  It seemed to be a fine for WiFi setups and nothing else.  But the cell signal dropped 2 bars and was often unusable.  After going through 4 of them (one was DOA), I found that it locked to the LOWER level signal (happened to the the 5G) and ignored the stronger LTE.  Engineering was totally clueless, like usual.

So I went back to the ASK.  Fortunately they had finally (it took over a year) fixed the IPv6 WiFi problem.  So I was happy.  But it's no longer supported.  They can't even send me a replacement battery for it now.

I haven't tried it, but wonder if this might get around the missing Bridge Mode:  Use your own router which also supports a VPN for you LAN.  This way the TM gateway would only see the router.  You would probably lose IPv6, however, since most VPNs still don't support it.

Note: The 3rd generation gateway is just as dumb as the 2nd gen Nokia.  A support person tried to get me to switch to it, saying that it did support DHCP but I downloaded the manual and it doesn’t.

Note: Mullvad VPN doesn support IPv6 and it runs WireGuard which shouldn’t be too had to set up on a good router.

Then, my only question is this:  What does it take to equal the capability and setup parameters that my Spectrum Cable Modem / Router has? 

AFAIK, these modems I am using in several locations that I support are pure plug and play.  I could simply move my whole network to another city another cable modem with a similar set up and the only changes would be the IP and other Gateway settings for that one connection to the first device, which is MY firewall, INSIDE my LAN. 

I just ordered the 5G home Internet hoping I too would be able to dump Spectrum. From the great information above, particularly regarding carrier grade NAT, I see I would have to totally revamp how I think about "internet facing" when it comes to my Pfsense WAN interface. I've depended on having a public IP on that box for IPSec purposes as well as some port forwarding. This will be a long and tricky road to finding ways that I can satisfy all my needs around this new architecture. This is especially the case since we (the customer) have no power in the upper layers. I hate working on my home internet because of this. Once you've been spoiled in the professional networking world where you can control everything from the public facing BGP routes of a company to a local workstation's RFC1918 address, it sucks to get stuck back into the "consumer" box. It sure would be nice to have that kind of power with my own home internet! I guess we're just going to have to collect our knowledge and work together to find new ways of accomplishing our goals within the bounds of new carrier tech which we cannot control. 😔