Thanks for posting this, as I was going to report the same thing. I couldn’t for the life of me figure out why I stopped having stable mt-daapd connections after a power outage and system restart.
For me to have stable connections to mt-daapd running on my linux box with avahi, I must run the following command:
ifconfig eth1 allmulti(where my primary network adapter is eth1, and I have a multicast route enabled).