MySQL authentication success depends on interface speed

I've been using LE with a common MySQL database for over a decade and have a standard advancedsettings.xml file which I copy across to each new system. When trying to setup a new Raspberry Pi 4, LE failed to connect to the MariadB database on my Synology server to populate the library display. Weirdly, after manually browsing files on the server a connection would sometimes be established and everything would behave normally. After a reboot however the connection was lost again. Browsing the log files shows that authentication is failing at startup for all tables in the database.

I tried to pinpoint the problem at the packet level using Wireshark on the PC - connecting the Rpi to a second (USB, 10/100) ethernet interface and bridging it to the main PC interface (Not straightforward BTW). Surprisingly, LE authenticated quite happily so I was then unable to record the problem.

I then plugged the 10/100 interface into the Rpi4 and used that instead of the built-in interface to connect to my GbE router - LE again authenticated properly.

It appears that the RPi4 will not authenticate to MariadB when connected using GbE all the way to the server. Inserting a 10/100 throttle seems to get around the problem - but will then restrict the media traffic to 100Mbit/s at best.

Platform:

• LibreELEC-RPi4.arm-11.0.6 & LibreELEC-RPi4.aarch64-12.0.2
• Hardware Platform: Raspberry Pi 4, 4Gb

Good call! I just discovered that the GbE port on my wall is only connecting at 100Mbit/s - the cable must have a broken wire somewhere. Connecting to a tested working port restores the usual expected behaviour. Very weird that the crippled connection transmits apparently error-free data for playing movies etc. but always refuses to authenticate the database on startup.

Thanks

Just been in my loft and mice have chewed a number of cables - and in this case broken the brown wire!!!!! I'd better test all the others.