So, my FreeNAS Server started randomly spewing my log file with this:
Dec 24 16:16:10 zoe kernel: arp: 43:05:43:05:00:00 is multicast
Dec 24 16:16:10 zoe kernel: arp: 43:05:43:05:00:00 is multicast
Dec 24 16:16:10 zoe kernel: arp: 43:05:43:05:00:00 is multicast
It was going at a rate of about 1 a second (in bursts of 5 every 10 seconds or so).
I fired up Wireshark to work out what it was, turns out it was my OpenMesh Wifi Access points sending these packets out.
Read more to see how I fixed it 🙂