· I'm having trouble with Roon ARC
· Other
arc is not connecting and is undersampling to my mobile dac device
netgear R9000 router,DOCSIS 3.1 modem model EN2251,spectrum router wifi 6 SAX1V1K
Continuing the discussion from Roon ARC not connecting and undersampling on mobile DAC (ref#TMH42Y):
The issue with ARC connectectivity is due to the presence of two (or more) NAT devices (routers) between the routable internet and your Roon Server. This can be caused either by multiple routers in your local network or by the use of CG-NAT by the ISP which is effectively the same.
Unfortunately, the screen shot of the ARC connectivity Diagnostics Data has truncated the line that may give more of a clue as to what is going on. Copying the text and posting it in a reply would be helpful.
However, I can see, from the screenshots that your Roon Server has an ip address of 10.0.0.2 and in another screen shot I can see that your iPhone has an ip address of 192.168.1.58. Both of these ip addresses are non-routable and so must be in your local network. This means that you have two subnets which is not a supported network configuration and suggests that you also have two routers (or possibly one router offering a segmented network - wifi guest network for example?)
Is the Netgear router the only router that you have? Is there another router provided by your ISP?
If you have more than one router, then you need to do one (and only one) of three things to fix it:
If this doesn’t work, you could, as an alternative, ignore the port forwarding issue and use Tailscale to set up a VPN that will allow your ARC device to connect to your Roon Server as if it was on the same subnet of your local network.
There is a help-centre article on the use of Tailscale at:
Using tailscale will completely bypass the need for port forwarding and will allow ARC to work even though the ARC connectivity report on the Roon → Settings → Roon ARC page will continue to report a port forwarding problem.
If you are certain that you only have one router then your ISP is probably using CG-NAT. You still need to find out why your iPhone is connected on a different subnet to your Roon Server and fix that so that they are on the same subnet.
What ISP do you use?
You can not fix the use of CG-NAT yourself - you have to contact your ISP and ask if they can supply a static, or at least routable, public ip address that supports port forwarding. Often this can be done - possibly with a monthly surcharge.
Again, using Tailscale will avoid this issue.
Your sample rate issue is probably because you are using the IOS mixer to output to the USB DAC. This forces resampling to 48kHz.
On Android devices, there is a setting in Roon ARC to enable a USB driver (beta status) which can bypass the OS Mixer and works for some. Is there an equivalent setting in ARC on iPhones for IOS? I don’t know, I don’t use Apple devices.
Incidentally, it makes things much simpler if you restrict yourself to one issue per post - especially when, as in this case, the sub-category that you are posting in is inappropriate to the second issue. With help for two or more issues being sought in one post, the thread conversation can get very fragmented and difficult to follow.
This subcategory (ARC: Port Forwarding Help) is appropriate for the ARC connectivity question but the sampling rate question should be posted in Support
On USB-equipped iPhones the DAC resolution should be accessible by default. I have an external DAC on my iPhone 15 and it just works without resampling.
In the photos it looks like a phone with Lightning connector, though, and I believe it is more complicated there. I don’t know about the details but there are plenty of forum threads.
· Yes, Roon Server is turned on and running.
· I see something else
· I see something else
· No, the issue remains the same
· No, the issue remains the same
· Roon Server is connected by *Ethernet*
· Roon still won't connect even after checking this aspect
· My Remotes and Server are on the same subnet and I still can't connect
· I've reinstalled the Roon Remote but it did not help
· *Windows*
· None of the above
Roon not outputting correct sampling rate to my iPhone which is connected to a ifi hip dac, I had this problem before but I do not Remember what to do to correct it
I have spectrum internet service my router is connected to spectrums router, my router I am using is a Netgear r9000
Hi @bradshaw4sb,
Thank you for your patience. The team is investigating with development for more detailed input and will respond shortly.
If iOS or ARC don’t register the DAC’s full audio capabilities, then automatic downsampling to the system output’s sample rate will occur. We’re going to investigate and attempt to reproduce the issue internally with our QA team. Can you please specify the year and model of this iFi DAC?
It’s a ifi hip dac 2, year dec 2023, Roon had always worked fine with this ifi hip dac and even when I had the previous model the original hip dac 1 and also it’s works fine in sampling rate directly from Roon and tidal, I had this problem once before and the Roon support to change some settings in my router to output all the proper sampling resolutions and I also am having trouble now connect to arc, also connecting this hip dac 2, directly to my pc and using Roon, it operates exactly as it supposed to with Roon
Let’s take a step back - you mentioned you’re having difficulty connecting to ARC itself.
Please share the full error diagnostic from Roon Settings → ARC? Your router settings won’t affect sample rate in ARC, but your router settings will affect RoonServer’s ability to reach ARC via port forwarding.
As for the iFI DAC itself - am I correct in understanding that you’d previously seen bit-perfect playback with ARC, but now see downsampling in the chain?
Hi @bradshaw4sb,
Thanks for the follow-up - as @Wade_Oram mentioned earlier in the thread (thank you, Wade!), your issue is due to the MultipleNatFound status. For next steps, can you please run through the following:
We’ll be on standby for your results. 
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