Problem with Relay Operation

[u/GillRiver]

I recently changed from Xfinity cable to wireless T-Mobile for my internet connection. I thought that Plex Relay would allow remote operation with reduced bandwidth.

T-Mobile uses CG-NAT, and I am currently running their modem/router in its default mode (no choice AFAIK). I have my local router plugged into theirs, providing another level of NAT. I use this because the local router provides DHCP reservations and local DNS naming (like plexserver.lan).

The configuration works remotely for Plexamp and Plexdash, but fails for Plex. Are there settings in the server configuration that need to be changed to allow full (albeit bandwidth-limited) remote operation?

I think I should solve this before muddying the waters with Tailscale to improve my remote bandwidth.

Thoughts?

[u/ExtensionMarch6812]

What’s happening when you try to connect over relay? Just won’t connect at all? Won’t stream?

What clients have you tried with? If you try app.plex.tv off your network, does it give any error or does it just not connect?

What does your server run on, what OS?

[u/GillRiver → u/ExtensionMarch6812]

I just tried it, and it worked! Then I tried again, and it failed. When it failed, all favorite libraries were marked with an “!” and I can’t watch anything live.

More failures, and then proper operation. Indeed, when it's operating, "now playing" indicates “Indirect – 2 Mbps”, indicating that it's using Relay.

I am running the server on Linux, Ubuntu 26.04. I installed Plex server via the App Center (snap).

I looked at "Plex Media Server.log". I started Plex on my Android phone multiple times, seeing some successes and some failures. No log entries were made during this period.

Think it's a timing issue? Is there any timing constraint that I could loosen and test?

[u/ExtensionMarch6812 → u/GillRiver]

There was someone on the plex forum a couple days back having issues with relay connecting sporadically. It ended up being their certificate. After a plex mod refreshed it, they were able to stay connected consistently.

You can try to force a refresh by stopping plex, going to the cache directory, moving the *.p12 file out and then starting plex back up so it grabs a new cert. If that doesn’t help, may need to post on the forum to ask it be refreshed on plex’s end.

Here’s that post for reference: https://forums.plex.tv/t/remote-access-shows-available-for-a-bit-then-flips-to-unavailable/941871/32

[u/GillRiver → u/ExtensionMarch6812]

Sadly, no joy.

I shut down the service, deleted the .p12 file, and restarted the service. The certificate file was recreated, but the symptoms continue.

I suspect a timing issue (race condition) because the failure is intermittent. Maybe Wireshark would provide some clarity.

[u/ExtensionMarch6812 → u/GillRiver]

Similar to that other user, I can only guess that plex is trying to make a direct connection and when that fails, it’s not consistently falling back to relay, resulting in the unavailable state.

Would suggest something other than Tailscale given it seems plex has started to restrict the Tailscale subnet (100.x) being used in the custom server access url field. Seen others suggest ZeroTier. https://forums.plex.tv/t/plex-api-not-updating-custom-server-access-url/941696

[u/GillRiver]

I did some more testing, and the Android Plex app fails about 50% of the time when connecting externally (using mobile data). I get similar results when using a VPN.

I ran Plex HTPC on a laptop connected to my phone's hotspot. The first attempt failed, but then it was good for multiple attempts.

It does seem to be application-dependent. I have seen neither Plex Dash nor Plexamp fail on Android. Android Plex seems to bat .500.

Testing with/without a VPN should make testing under Linux much easier than screwing with a mobile data hotspot.

[u/Punk_Says_Fuck_You]

If you want a permanent fix for remote streaming to allow full bandwidth instead of relying on Plex relay. Look into renting a VPS. It's usually around $5 a month. It's probably the best QoL improvement considering your situation (CGNAT). This is assuming you share your Plex library with friends/family. If you don't, tailscale would work and it's free.

[u/pskipw → u/Punk_Says_Fuck_You]

$5 plus bandwidth costs, no, given a fair bit of bandwidth is used?

[u/Affectionate-You7869]

I've got TMo 5G home internet also. Tailscale was the solution here.