[Flint 3] Port Forwarding and DMZ randomly stopped working

[ReticentRobot]

I run a Plex server so that my wife and I can use Plexamp to listen to our music when outside of the house. Last Friday it stopped working, and Plex is now reporting that it is inaccessible to remote access. I hadn't changed anything in the router, and double checked that port forwarding for it was still in the settings in my Flint 3. I also tried changing it to DMZ instead and that also didn't work. Checked a couple of other open ports (not Plex) while it was in DMZ (moved it back to port forwarding afterwards) and those also reported as inaccessible outside of the LAN. I contacted my ISP and they assured me that they have not started blocking anything and still have a no port blocking policy. I also took down the firewall on the server completely to make sure it wasn’t causing the issue, but that didn’t help either.

[RBzee]

When you go to whatsmyip, does it match the Public IP shown in Plex?

Also, is your Plex server on a NAS or PC?

Edit: I disabled Network Acceleration on my Flint3 a while back. It was causing random connectivity issues.

[will.qiu]

Hi

If you connect your Plex server directly to your ISP modem to obtain a public address, does this issue occur?
If the problem persists, it may be related to your ISP.

If the issue doesn't occur, please put the Flint 3 back and let us know:

1. What is the current firmware version of Flint 3?
2. Try deleting the old port forwarding rules and recreating them to see if that resolves the issue.
3. If not, please SSH into the router, run the following command, and share the results with us:

nft list ruleset

4. Install tcpdump and capture packets to verify port forwarding functionality:

opkg update && opkg install tcpdump
tcpdump -i eth0 tcp port 32400

After packet capture begins, kindly attempt accessing the service from the external network multiple times.

[ReticentRobot]

Thanks everyone. I verified with my ISP that they just implemented CGNAT, so looks like that is the problem and not the router. Looking into what my options are now.