MAC addresses, one for each network connection.

The undefined entries drop off after a while on their own accord, alternatively you could pull the power from all your SONOS devices but personally I would not bother.

Thanks for the info…. do you happen to know… do all the sonos devices keep a record of this kind of thing…. or is it just one that acts as the master? 

‘24:A6:D8 is the internal MAC (and matches the serial number).

‘24:A6:D9 is the wireless MAC (which is disabled).

As with your other recent query, a little knowledge when poking around in the diagnostics can lead to confusion. These pages are not designed to be user friendly. If the system is behaving itself then ignore them. If the system is causing problems there’s insufficient user-visible data to effectively diagnose. You’d need to submit a full diagnostic for Support to examine. 

Thanks. I appreciate it. Although I'm a long time user, I've only recently started getting annoyed by the dropouts. New house is bigger and I don't think the WiFi that used to be ok can cope with 1 the new house and 2 the number of devices that saturate the network now

I had issues with my WiFi setup and found a wired Sonos device and SonosNet to be a superior solution.

The other thing that I found extraordinarily helpful in the past was assigning reserved IP addresses for all my network devices, including my Sonos. I had a relatively inexpensive router that tended to lose where it was in the DHCP table every time I either lost power, or Sonos did a software update. I finally replaced the router, but set up reserved IP addresses in the new one, too.