Screens connect with Wireless Modem - Double-NAT issue

Hi all,

I’m trying to use Screens Connect to access my Macbook Pro using my iPad. I have an Optus wireless modem E5573 that I use to connect to the internet.

As per the Screens Connect guidelines, the modem supports UPnP.

However, Screens Connect keeps giving me a fatal error: “Setup cannot continue. Please check your router configuration. Double-NAT issue.” Clicking “More Info…” takes me to this page. However, I don’t find any of the possible solutions helpful, because I’m not using a dual modem/router setup. I just have a portable wireless network with internet that my laptop connects to!

Has anyone tried using Screens Connect with this setup before, and had any success? My understanding of networks and port forwarding is limited, and I don’t want to fiddle with manual configuration or other stuff like that without someone holding my hand through the process, lest I accidentally leave myself without internet access.

Edit: a little research suggests that port forwarding is unavailable on my wireless modem.

Is this Optus modem the only networking device you are connecting to or is there an other (wifi) router involved.

UpnP is a very insecure feature and its highly recommended to disable it!

As per that post you linked to.

“All the Optus personal mobile connections go through a “symmetrical NAT”, which scrambles everything. There is no way to connect to it externally, because each connection ends up being through a random port that it decides. They can only ever do outbound connections to servers”

This is not about the Optus data but about the fact that UPnP is easy to be compromised so that bad 3rd party actors can open ports, route traffice etc etc trough your internet connection.

@MacExpert - Yes, it is. I have an old Netgear router in the shed somewhere, but based on the symmetrical NAT, looks like this won’t help.

@abeardy - You’re absolutely right - how did I not see that!

I am not familliar with this Optus connection. Sounds like a nightmare to me…

Set your Netgear router in “Bridge Mode” and try again. I would be very surprised if Screens starts working right away.

Either way its strongly encouraged to disable UPnP on any network device and do the port mapping / forwarding manually.

1 Like