Unable to connect to ARC despite UPNP and port forwarding attempts (ref#YRM9N6)

[Geoff_Ley]

Network Setup

· I use a single personal router not provided by my ISP

ARC Status

· ARC is *Not Ready*

Roon Error Code

· “natpmp_autoconfig”: {“status”:“NotFound”}, “upnp_autoconfig”: {“status”:“NotFound”} }

Have you successfully located and enabled the UPnP or NAT-PMP settings in your router's web UI?

· I've turned UPnP/ NAT-PMP on and ARC won't connect

Select the Diagnostic Keyword or Text String

· Something else

Don't give up yet.

· I'm stuck. I'd like to create a post to ask Roon Community for help.

Describe the issue

Have tried UPNP and port forwarding. Cannot connect to ARC

Describe your network setup

ISP: Leaptel Australia, Unifi UCG Ultra router, non-managed switch, ethernet

{
"ipv4_connectivity": {"status":"NetworkError","status_code":526,"error":"error code: 526"},
"external_ip": {"actual_external_ip":"202.aaa.bbb.ccc","actual_external_ipv6":"null","router_external_ip":"null"},
"natpmp_autoconfig": {"status":"NotFound"},
"upnp_autoconfig": {"server_ip":"192.168.1.1","found_upnp":true,"error":"doaction request return statuscode: UnknownError"},
"multinat_autoconfig": {"status":"Failed","error":"No uPnP Routers found on LAN"}
}

[vadim]

Hi @Geoff_Ley,

Welcome to the community!

You are hitting a “perfect storm” of three potential issues here: a known display bug in Roon, a likely ISP configuration, and a UniFi-specific quirk.

Here is how to break them down:

1. The “False Negative” Check (Error 526)

First, we are currently experiencing a display glitch where Roon Settings reports Error 526 and “Not Ready” even when ARC is working perfectly.

• Please test this first: Turn off Wi-Fi on your phone and try to play music via ARC over cellular data.

• If it works, ignore the error message for now.

• If it fails to play, proceed to step 2.

2. The ISP Check (Leaptel & CGNAT)

Leaptel (like many Australian ISPs) often uses CGNAT (Carrier Grade NAT) for residential connections. This means multiple customers share one public IP address, which makes Port Forwarding impossible, regardless of your router settings.

• How to check:

  1. Log into your UniFi Network Dashboard.

  2. Go to your Internet / WAN settings and look for your WAN IP Address.

  3. Compare this IP address to what you see on a site like whatismyip.com.

• The Verdict:

  • If the UniFi WAN IP starts with 100.x.x.x (or 10.x.x.x), you are behind CGNAT.

  • Solution: Contact Leaptel support and ask to “opt-out of CGNAT” or request a static public IP. They are usually very helpful with this.

To bypass the CG-NAT restrictions, we are offering the Tailscale solution more information, you can find here:

ARC and Tailscale: Connect to RoonServer Without Port Forwarding

[Geoff_Ley]

Thanks Vadim,

I was aware of the “false negative” and tested for it before submitting my support ticket. You were also correct that my ISP uses CGNAT by default, but I logged into their portal and turned it off since my earlier error messages were indicating that this was a problem. Today, mysteriously, ARC is working. I haven’t changed anything since I contacted you last night, but the last change I made was to revert to UPnP and disable port forwarding (I had tried both ways many times before). Perhaps my router took some time for the changes to be reflected. You mentioned three possible issues in your reply, including one that was a quirk with Unifi, but you didn’t actually list point three or tell me what the quirk was. Could this be it?

Thanks again for you your help.

Regards,

Geoff

[noris]

Hello @Geoff_Ley ,

Thanks for letting us know that ARC is working. The 526 error was due to the recent server-side outage, glad to hear that everything appears to be working properly again!