Network Error Detected: Multiple NAT Found and Router Control URL Missing (ref#7O22JT)

Support
1

Network Setup

· Do you have a mesh network? (Google Mesh, Eeros, Ubiquiti, etc.)

ARC Status

· ARC is *Not Ready*

Roon Error Code

· The ARC settings page says "Not Ready," but I can still connect to ARC via cellular data. I'm having another problem.

Describe the issue

{
"ipv4_connectivity": {"status":"NetworkError","status_code":504,"error":"error code: 504"},
"external_ip": {"actual_external_ip":"66.aaa.bbb.ccc","actual_external_ipv6":"null","router_external_ip":"10.100.13.46"},
"status": "status": MultipleNatFound
,
"natpmp_autoconfig": {"status":"NotFound"},
"upnp_autoconfig": {"server_ip":"192.168.4.1","found_upnp":true},
"multinat_autoconfig": {"status":"Failed","error":"Router Control URL not found"}
}

Describe your network setup

T mobile fiber model and Eero mesh network, roon arc used to work, but now has not for almost a year.

2

If you can connect and use ARC using cellular data, then there is nothing wrong with your ARC setup.

This clearly indicates that you do not have a functioning port forwarding setup and you have multiple routers. Thus, since ARC is working on Cellular data, you must have a Tailscale setup such that Access to your Roon Server from the ARC device is performed across the Tailscale tunnel as if the ARC device was connected to the home network.

If you are using Tailscale, this status indicator is irrelevant since it only relates to external ARC connectivity employing port forwarding and the whole point of Tailscale is that it bypasses the need for port forwarding.

As a result, if my understanding is correct and ARC is working and you are using Tailscale, then the ”ARC is *Not Ready*" status indicator and the diagnostic text that you have posted can be ignored because they have no significance.

Alternatively, if I have misinterpreted your post then please clarify and I, or others, will try to help further.

3

Hello @Aditya_Rudrakshi,

Wade is absolutely spot on regarding the root cause, but if you don’t actually have Tailscale configured yet and ARC is just acting up or working intermittently, here is how you can completely fix this diagnostic error.

The logs clearly show a Double NAT issue: your T-Mobile fiber gateway is assigning a private IP (10.100.13.46) to your Eero mesh router (192.168.4.1), which blocks the standard UPnP/Port Forwarding from reaching the internet.

Option 1: Fix the Double NAT (The Standard Way)
To get Roon ARC working natively without third-party tools, you need to eliminate one of the routing layers:

  • Method A (Recommended): Log into your T-Mobile fiber gateway's web interface and enable Bridge Mode (sometimes called IP Passthrough). This turns the gateway into a simple modem and allows your Eero to handle all the routing and port forwarding directly.
  • Method B: Alternatively, open your Eero app, navigate to Settings -> Advanced -> DHCP & NAT, and switch it to Bridge mode. Note: This will disable some advanced Eero features like Eero Plus, as the T-Mobile gateway will become your primary router.
Option 2: Use Tailscale (The Bulletproof Bypass) If you cannot change your hardware settings, or if T-Mobile uses CGNAT that prevents port forwarding altogether, you can bypass the issue completely using Tailscale. It creates a secure encrypted tunnel between your core and your mobile device. Since your Roon Server is likely running on Windows, you can follow the official step-by-step setup guide here: [url=https://help.roonlabs.com/portal/en/kb/articles/tailscale-setup-instructions-windows-roonserver]Roon Labs Help Center - Tailscale Setup Instructions[/url] Once Tailscale is up and running on both your server and your phone, you can completely ignore the "Not Ready" status and the MultipleNatFound error in Roon - ARC will work perfectly anywhere .

Let us know, please, if any of the suggested ways fix the problem for you.