Complex Network Blocking Local Plex Access

Plex Media Server
1

Server Version#: 4.156.0

I’m having a very unique problem. I suspect an update to the Plex server or the way users are handled from the mothership is stopping the SmartTV from accessing my library. This actually did work at one time, but no longer does with a message that the Plex server could not be reached and could be down. I’m pretty sure this is related to how my network is set up. Believe me, there’s a reason I have it this way!

Here is a simple diagram:

                    ┌────────────┐                      
                    │  INTERNET  │                      
                    │            │                      
                    └──────┬─────┘                      
                           │                            
┌─────────────┐    ┌───────┴───────┐   ┌───────────────┐
│             │    │               │   │               │
│ 192.168.2.x ┼────┤ 192.168.100.x │   │  192.168.0.x  │
│    Router   │    │    Router     ├───┼     Router    │
│             │    │               │   │               │
└──────┬──────┘    └───────────────┘   └───────┬───────┘
       │                                       │        
┌──────┴──────┐                        ┌───────┼───────┐
│             │                        │               │
│   SmartTV   │                        │     Plex      │
│             │                        │               │
└─────────────┘                        └───────────────┘

I have 3 users in Plex Home. 2 of the users are on the same network as the Plex server and there are no issues. The 3rd is in the segregated nework. The SmartTV in the 192.168.2.x at one time could access the Plex, but as of a few months ago could no longer. The router on the 2 network and the 100 network are D-Link and TP-Link, respectively, so I’m limited on what can be done on those two routers.

Yes, the network needs to be this way. There’s a lot more going on, but this is the path that’s the problem.

My guess is that there was a change in how Plex Home users connected and likely started their connection by going from the SmartTV through the internet to Plex, coming back down and then, somehow the direct connection between the two got made. I’m thinking because of a change Plex made on one side or the other, the SmartTV looks like a remote system and is being blocked because of that. Again, that’s just a guess.

Is there a way to make this work again? I understand this a very far out of left field configuration.

2

There might be alternative firmware for certain models from these manufacturers. If your devices are among the supported models, using these alternative firmwares could substantially extend their configuration options and abilities.
For instance: https://wiki.dd-wrt.com/wiki/index.php/Supported_Devices

Your diagram shows your server machine in a typical double-NAT situation. Unless you have a special route configured which allows the .2.x to access the .0.x network directly (which is unlikely, given the default firmware abilities of these consumer routers), the client in the .2.x network will need to use the remote access to your server.
Which in turn means you need to ensure that remote access is functional. The double-NAT makes this more laborious, but the good news is that a double-NAT can be traversed, but you need to establish manual port forwardings in both the .100.x and the .0.x routers. i.e. you need to access the configuration of both routers.

The main router .100.x needs a port forwarding from external port number “X” to internal port number 32400 directed at the IP of the .0.x router. Keep in mind that you want to reach the WAN/external interface of the .0.x router, which means its IP is in the 192.168.100.x range.

The .0.x router needs a port forwarding from external port 32400 to internal port 32400, directed at the IP address of your Plex server machine.

Then you edit your Plex server settings and put the external port number X into
Settings - Server - ‘Show Advanced’ - Remote Access - “Manually specify public port”
The actual number you should use for X could be any non-privileged port number between 20,000 and 50,000.
I recommend you to NOT use the well-known Plex port 32400 for X.

Caveat: if your ISP has put you behind a Carrier-Grade NAT, you are out of luck. Because you don’t have access to your ISP’s routers, so you cannot establish the necessary port forwarding. The only chance in this case is to ask your ISP for a publicly accessible IPv4 address. Most ISPs will require you to shell out additionally for a “static IP address”, if you want one.