Comment 46 for bug 94940

I think I have found some of the problem. avahi-daemon gets into a weird state when it sees advertisements for both IPv4 and IPv6 addresses for the same service. You will notice that when you run avahi-resolve just after ifdown/ifup, you will be given an IPv6 address. About 2-8 seconds later that same request yields and IPv4 address.

The caching behavior of avahi-daemon appears to allow this to occur about every 8 minutes, from my own testing. ssh (but not ping) is vulnerable to this and will report that the server in question is down. This will of course happen for rsync as well.