Looking at all these posts I am still a bit confuzed… I make a switch, DeJitterIt Switch X, that also does NAT and as expected ARC can’t traverse this. A double NAT of course can’t do UPnP or NAT-PMP.
But I would think a double port forward would work ? On the internet facing NAT set a port forward to the 2nd NAT. On the 2nd device set a port forward to the roon server. While this requires all the 2nd NAT and roon to be on DHCP static or fixed IPs this should work fine ?
I would of course either use a whole different port # for security or I could do port translation with the fwd on the internet facing side and have the app on that port ?
This then no longer relies on UPnP or NAT-PMP and should be quite stable and work ?
I was unsure about a double port forward solution as i have not seen that covered.
The part that gave me pause was this line from the below Multiple NAT section on this support doc…
"The important part is here:
“multiple_nat”: {“actual_external_ip”:“100.37.159.105”,“router_external_ip”:“192.168.1.108”}
As you can see there are two different external IP addresses shown – “100.37.159.105” and “192.168.1.108” which indicates that your server is running behind a multiple NAT configuration.
In this case, you’ll need to ensure that only one of your devices is providing NAT. "
Which is pretty final… But I assume that is referring to UPnP auto config and if you set up a manual port forward none of this matters.
If you’re creating a manual TCP port forwarding rule in your router(s), then you won’t need to rely on UPnP at all.
However, if UPnP reported to Roon via the diagnostic code that the router’s WAN IP did not match the actual external IP address for your account, then that’s a strong indication that your internet service provider is translation your WAN IP address upstream of your account. That is carrier-grade network address translation (CG-NAT), and unfortunately, there’s no setting you can change internally to your network to bypass it.
If you’re still having trouble connecting after creating a manual TCP port forwarding rule using the port and IP address in Roon → Settings → ARC, then you’re likely stuck behind CG-NAT. Who is your internet service provider? You can likely reach out to them to inquire if a dedicated external IP address is available.