With all SSDP based services I can find disabled Plex multicasts M-SEARCH packets every 10 seconds to 239.255.255.250 This behavior seems new to FreeBSD version 1.3.3.3148. Came up beause, like many comcast routers, one of the two I have under test here stops throwing packets for ~1.5 seconds each time it sees an M-Search packet. After updating plex latency problems came up again, previouslky solved by disabling SSDP services on plex.
You can replicate the behaviour by unchecking “Enable DLNA” in Settings -> DLAN, unchecking “Enable local network discovery (GDM)” in Settings -> Network. Then run a packet sniffer on the same network as the plex server searching for UDP Port 1900 packets.
A very few would be generated by checking “Manually specify public port” in Settings -> Remote Access, but those should be few and far between and shouldn’t result in a packet every 10 seconds.
Forum will not allow me to attach logs, I’ll try again in a while.