Plex is not reachable - caused by router?

General Discussions
1

Hey, I’ve been having some issues recently - please bear with me as i try to explain.

I had PMS running on an Ubuntu 16.04 LTS box for a few years without issues. In the past month I started getting the ‘Plex is not reachable’ page when trying to access the server through Plex.tv and the machine’s local IP.

I spent a little time troubleshooting after reading some of the many issues people were having when disconnected from the internet, but in my case the server always had a connection. After removing the Preferences.xml file I could access the server with the local IP but when trying to log in (using the upper right menu in Plex/Web) I would get the ‘Plex is not reachable’ again. If I tried logging in from the server settings I would receive a nondescript error message (sorry I don’t remember the wording).

Anyway, I decided to cut my losses and overhaul the box as I had been planning to to for a while anyway. I installed CentOS 7 and the linuxserver/plex docker image, and to my surprise the default fresh install showed the same issue. If I tried to log in I saw the dreaded ‘Plex is not reachable’ page, and if I copied over my old server settings I was back to square one.

I stopped docker and installed the vanilla downloadable version and still saw the same results.

At this stage, I stumbled upon a ‘solution’ - if I rebooted my router, the problems went away - at least for a while.

After this long-winded explanation (sorry!), my question is this: what could be causing this within the router?

I use the default port of 32400 which is manually forwarded within the router, and regardless of this issue people can still connect to and stream from the server. I also have upnp enabled on the router ‘just in case’ but don’t see any ports being opened by PMS. I looked up any secondary or potential other ports that PMS might want/need and drew a blank.

Does anyone have any ideas of what this may be?

For the record, my router is a Fritz!Box 7490 running the latest firmware; and while I agree that this appears to be a fault on the router side, what could be happening/not happening on the Plex side to throw this page?

Thanks for reading, and I appreciate any thoughts!

2

Same problem for me. I usually get 2 minutes of it working after a reboot, but then it is unreachable
Again.

3

Hey M&A, which router do you run? It might be partially useful to see if there is any correlation.

4

@eep I think you need to take a look a the link below:
https://en.avm.de/service/fritzbox/fritzbox-7390/knowledge-base/publication/show/663_No-DNS-resolution-of-private-IP-addresses/

5

Interesting, thanks @“Ach!lles” - DNS rebind protection is something i know very little about. Could this affect connections from inside the local network, using the local IP of the server?

Frustratingly, my issue is sporadic, and until it happens again I can’t fiddle!

6

Yes. You can confirm that by turning off require secure connections in PMS. Refer to this support page:
https://support.plex.tv/hc/en-us/articles/206225077-How-to-Use-Secure-Server-Connections?mobile_site=true

Problema con FRITZ!box 7530
7

I really appreciate the pointers Ach!lles, thanks!

In my router settings I have a ‘DNS rebind protection domain name exemptions’ field. Adding plex.direct to the field appears to be what is required.

Thanks again!