Any thoughts on where/how is this 'home in' state is saved? Other the cache and filtering/acl state resolvers should be stateless, so would be interested in any details, especially if this is on a per-zone, or per-set of nameservers or etc basis. I've never seen bind9 act like this.
BIND assigns a score based on every IP it talks to and a hit rate. (so if ns1.foo.com resolves to 3 IPs, each is tracked individually, same if ns1.bar.com and ns1.baz.com are the same IP) It is a pretty small cache, maybe like 1024?
