On Fri, 13 Feb 2026 14:33:53 +0100 john doe <[email protected]> wrote:
> On 2/13/26 9:33 AM, john doe wrote: > > On 2/12/26 22:42, [email protected] wrote: > >> Background: I switched to T-Mobile for my Internet connection (via > >> 5G) and, as > >> far as speed and lack of interruptions, it works fine for me, but > >> I have a few > >> problems: > >> > >> * I'm not asking about this, just noting it: The address of > >> the TMO-G4AR > >> device is 192.168.12.1 and cannot be changed (and certainly not > >> from the .12 > >> "subnet" (right word?)), which meant I had to reconfigure all my > >> devices, some > >> of which I forgot how to do.:- > > > > > > Why, were you having IP conflict/why did you have to change the > > IPv4 addressing of your network? > > > >> ( (Ok now ;-) > >> > >> * The TMO-G4AR device is not a router, but it does NAT (I > >> think it does > >> DHCP also, but I'm not using that at all, I use static (IPv4) > >> addresses), does > >> not do routing, and cannot be switched to bridge mode. > > > > How did you determine, the service(s) that are running on your ISP > > "router"? > > > >> Trust me on those things that the TMO gateway device cannot do. > >> There are > >> some ways to get a different device that works on the T-Mobile > >> network which > >> can do (some of?) those things, but requires switching to a > >> "business license" > >> at a higher cost and paying for thruput. > >> > > > > Can't you simply use your router/modem? > > > >> I had my devices working for a while (a few months) but had no > >> occasion to do > >> anything like ssh between them. Today I had a need and realized > >> that I cannot > >> ssh (or ping) between them because the TMO does not do routing. > > > > YOu are using static addressing, so you should be able to talk to > > one another. > > > >> > >> The question(s): I have a Ubiquiti Edge Router X which I used with > >> my previous > >> cable based ISP. I'd like to add it back to the LAN to enable > >> communications > >> between devices, but because the TMO device does NAT and so would > >> the Edge > >> Router, I'll have a double NAT setup -- I'm worried about that > >> especially for > >> my VOIP communications. > >> > > > > Just try with double natting for now and see how it goes.. > > > >> I'm thinking about 2 (or maybe 3) solutions. > >> > >> 1. The simplest for me to explain is to put a 2nd Ethernet > >> interface in each > >> of my computers and then run one Ethernet interface (through a > >> switch) to the > >> TMO and the other Ethernet interface (possibly through another > >> switch, depending on where I locate the router) to the router. > >> I'm guessing that > >> could be made to work, but that it would require some "gymnastics" > >> to routing > >> tables in each computer (or something along those lines). > >> > > > > An option but why.. > > > >> 2. The slightly more complicated one for me to explain is to > >> somehow stick > >> with one Ethernet interface per computer, run each to a switch, > >> and have those > >> switches interface to both the TMO and the Edge Router. Again, > >> I'm guessing > >> this could be made to work, and would require "gymnastics" of some > >> sort. > > > > Like above, I would say router from ISP Edge Router, switches and > > than your devices. > > > >> 3. Another possibility that I'm not real comfortable with, but > >> maybe could > >> work: The TMO-G4AR has two RJ-45 connectors that can be used to > >> connect to > >> "network segments". > > > > > > How do you know that? > > > > You don't know the services running on your ISP router.. > > > >> I could set up the Ubiquiti to handle communications on > >> my LAN and also connect to one of those TMO connectors to provide > >> access to > >> the Internet (for the LAN), and use the other TMO connector to > >> connect my (hardware VOIP devices) without a router, thus no > >> double NATing for those. > >> > > > > I do not trust something from my ISP, connect your Edge Router to > > your ISP router and disable natting on that Edge Router. > > This assumes that you can set static routes in the ISP router. > > > >> I do also use google voice VOIP from some of my computers, and > >> that would be > >> subject to double NATing. > >> > >> I don't play games or such, I do have one (smart) TV connected to > >> the TMO (currently via the LAN) that I watch sometimes in the > >> evening. Thus, except > >> for the VOIP lines, I'm not sure I have much to worry about with > >> double NATing. > >> > >> At the moment, I'm throwing these possibilities out for any > >> comments you have > >> to offer, and to help me pick the path going forward. > >> > >> Oh, one other thought: in my readng on the Internet, at least one > >> person suggested that switching to IPv6 could resolve my (or > >> somebody's ;-) problems > >> -- if that is a solution, I might consider it. (IPv6 is Greek to > >> me, and I've > >> resisted it up-to-now because I feel somewhat secure behind NAT > > > > NAT simply ensures that private IPv4 addresses are not routed on > > the internet, that has nothing to do with security! > > > >> (and because > >> it is Greek to me).) (Oh, related to that, I have no idea what > >> the TMO device > >> would do with IPv6.) > >> > > > > YOu are already lost with IPv4, stick with it! :) > > > >> Once I pick the path, I'll almost surely ask for more help for > >> things like > >> setting up the routing tables appropriately. > >> > >> > > > > I would like to point out that this has nothing to do with Debian. > > > > First you need to understand what capabilities the ISP thing > > provided by your ISP does or see if you can have your own cable > > modem. Does the box that you have now from your ISP has build-in > > wireless? > > > > If you can not have your own cable modem or set that ISP thing in > > bridge mode, look if you have a DMZ capability and add the Edge > > Router in that DMZ. > > > https://www.t-mobile.com/support/home-internet/5g-gateway-g4ar > > This assumes that you haveTmobile "home internet" > https://www.reddit.com/r/tmobileisp/comments/15z7j1g/new_gateway/ > > If the above two links matches what you have (device and plan) you > can not avoid double NAT. > > Based on the above, plug your own router behind your ISP thing and > your network behind your own router (double SNAT) and see how it goes. > I haven't done VOIP but I have done PPTP VPN through double NAT at each end, no problem. That is forwarding both a TCP port and another Internet Protocol. -- Joe
