T-Mobile (US) 5G Home Internet: CG-NAT Blocks ARC, Workarounds Required [Ticket In]

Roon Core Machine

Intel NUC7i7BNH (Intel Core i7)
Crucial RAM 32GB DDR4 2666 MHz CL19 Laptop Memory CT32G4SFD8266
Samsung 970 EVO Plus SSD 500GB

Networking Gear & Setup Details

T-Mobile 5G Home Internet Gateway - Arcadyan KVD21
Not using a VPN

Connected Audio Devices

Number of Tracks in Library

Description of Issue

In testing Roon Arc with my T-Mobile 5G Home Internet Gateway, I’m receiving a “Not ready” error with the following diagnostics data:

“connectivity”: {“status”:“NetworkError”,“status_code”:504,“error”:“error: Error: ETIMEDOUT, response code: undefined, body: undefined connected? undefined”},
“external_ip”: {“actual_external_ip”:“xxxx”,“router_external_ip”:null},
“natpmp_autoconfig”: {“status”:“NotFound”},
“upnp_autoconfig”: {“status”:“NotFound”}

I don’t know whether or not it is possible to enable UPnP or NAT-PMP with this Internet gateway as the settings menu is extremely basic and doesn’t list anything related to advanced options such as NAT or port forwarding. Please bear in mind that this is a modem, router, and access point combined in a single device which connects to the Internet using T-Mobile’s cellular network in the US.

Thank you for your help.

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Unfortunately it may be that TMobile 5G does not provide a routable external IP address. I know that this is true for many cell carriers with traditional WWAN routers. Also in general, it may be simpler to just manually configure port forwarding. That’s what I did with Xfinity Cable and my Untangle FW. Works great!

Same issue. I’d appreciate a step-by-step workaround, as I’m definitely not an IT person.

Same issue. Any help would be appreciated.

I just spent an hour on the phone with T mobile. The help desk supervisor ended up telling me that the T-Mobile gateways don’t support port forwarding and basically you can’t set up ARC with their system. We. Will have to wait for a software update or even a hardware upgrade in the future. Until there, stay home…

See the posts reporting on successful using VPNs, in particular Tailscale. This this will work without port opening / forwarding and routable external IP address.

@Vince_Galet - Just to let you know. I am using Deutsche Telekom ADSL with FRITZ!Box 7590 and it works fine.

Thank you both for your replies but I am limited to the hardware I have: Roon nucleus (I can’t configure anything there like VPN) and T-mobile router (where I can’t really see any configuration options either. It is more designed to be plug and play). I’ll try to find those VPN posts but I’m not very hopeful.

Same issue here. Following…


Hi @Vince_Galet and all,

Unfortunately, it’s true that the particular IPv4 tunneling implementation used by T-Mobile 5G residential tier accounts doesn’t preserve port assignments, so returns from your mobile device using ARC are filtered out and unable to reach the Core. This will manifest as the frustrating experience you’ve been facing for these last months: endless timeouts in Roon → Settings → ARC, and a “Can’t Find Your Core” screen in ARC outside your local network.

This particular situation is further complicated by T-Mobile’s Arcadyan gateways, which do not support UPnP and do not allow for manual port assignment.

In short, Roon users with your internet setup are stuck without ARC outside the home for the time being. From the team side, we have an urgent and high-priority initiative to allow ARC to function with IPv6 addresses, among other tickets to ease up the obstacles presented by common CG-NAT. We anticipate this will solve many major ISP-level blockages with ARC or otherwise open up supported workarounds. The team will be posting notes in our general tracking thread for ISPs and carrier-grade NAT issues here: ISPs and Routers: List of Known Solutions and Workarounds

Download local content in offline mode will function, and while many VPNs will require installing software on your RoonServer device, it’s always worth exploring some of the #tinkering discussions like this one: Mobile Use: Roon 1.8/2.0 via VPN vs. Roon Arc


Happy to help anyone needing advice.:grin:

PM me to save filling up this thread.:+1:

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Thanks Connor - not good news but this clarifies a lot, and there is hope that eventually this can be addressed.
When posting solutions/workarounds as they become available, please

  • identify T-mobile in the tile
  • keep in mind that many of us (including me) are not techies so we need step-by-step dumbed-down instructions like you would teach your mother
  • and not everyone is using a PC: in my case I am using a nucleus + and an ipad to drive it, so I can’t get in there to tweak things, and I can’t implement a crafty fix designed for PC. Again, I need something simple .
    I don’t mean to be demanding with the above, I’m just a computer-ignorant end-user (and music lover) at the mercy of technology (and those who know). Thank you very much indeed for helping people like me. Really appreciated!

Same issue for me here. Unfortunately this service is my only means of internet so I would love to be able to use ARC

3 posts were split to a new topic: Airband (UK) with Mesh System (Linksys): ARC Port Forwarding Failures

Useful information–thanks. I’d switch internet providers, but T-Mobile’s just so good in many other respects. I want to have my cake and eat it too. Too much to ask? Apparently it is at the moment.

I hope whatever workaround you come up with will apply to Nucleus and ROCK users like me.

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I am using Tailscale and it works well. But VPNs are weird at times I feel like. Feels like it slows my network down.

Hi everyone,

We’re continuing to make progress with our efforts to allow for more complete IPv6 compatibility with Roon ARC. Ideally, this would relieve a large swathe of CG-NAT issues trapping users on major networks like T-Mobile. We can’t guarantee it will help every user, but we are working hard to open access to ARC to our full user base.

@AvilleAudio, don’t worry, any solution we come up with will work for RoonOS Core users.


Glad there is a solution being worked on at Roon. Thanks @connor on this update and on my post as well.

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