Plex sending discovery traffic from the wrong source IP

[cyprien]

Server Version#: 1.41.2.9200

I noticed recently a lot of traffic from 169.254.70.194 to 169.254.255.255 on the Plex discovery ports (UDP/32412,32414). It turns out 169.254.70.194 is the IP of my LAN2 interface on my Synology DS918+ (DSM 7), which is not connected to any cable (which is why it has a link local IP).

It appears Plex is using the source IP of LAN 2 and sending the traffic out LAN 1. LAN 1 has a correct IP in 192.168.1.x.

I then unchecked “Enable local network discovery (GDM)” but I continue to see this traffic coming from the synology box.

Any other idea how I can prevent this flooding? This could also be a synology issue, I’m also troubleshooting this on the synology side of things.

[cyprien]

ok, so researching a bit it seems there’s two issues, one plex and one DSM 7.2.

Synology DSM 7.2 Spoof Network messages

[Screenshot 2023-07-19 083436] Server Version#: DS1821+ DSM 7.2-64570 Update 1 Player Version#: 1.32.4.7195-7000 Spoof message from Plex every 15 minutes or less. We have been talking to Synology over this issue for some time, there have decided that we should pass on to Plex. After a long investigation, we’ve discovered that Plex is sending out the messages on random ports. On network ports that are disabled I’ve tested this on a different Synology NAS running DSM 7.2 by installing Ple…

Plex Flooding 32414 and 32412

Somehow, when it did a “GetIP” call, it returned the IP address of that class A. The IP is returned by: PMS sends to Plex.tv from the host. Plex.tv sees the sender’s IP address Plex.tv returns that as the IP of the host. Pretty basic.

Utilising non-default interface

Indeed, why didn’t the simple step occurred to me, thank you! The issue was caused by the “Client Device Isolation” setting turned on on the WiFi portion of the 10.0.20.0/24 network. Connecting from a wired client on that network was immediately successful. Not really. The ADVERTISE_IP and Preferred network interface settings don’t do that. Multihomed hosts almost never work the way people expect. Without using additional fancy OS-level stuff, there’s no form of source-based or policy-base…

https://old.reddit.com/r/synology/comments/wqr934/router_spammed_with_dhcp_calls_from_disconnected/

• Issue 1: Plex continues to send discovery traffic, even if “Enable local network discovery (GDM)” is uncheced. This error seems 10 years old.
• Issue 2: Synology 7.2 seems to mess up something with multihomed devices, as shown in reddit link above.

I’m open for any ideas.