google has a huge number of hits, you really couldn't find anything?? http://www.tacktech.com/display.cfm?ttid=323
1. so people can't change your dns records without permission.
2. read up on the docs as in link above
3. what error? there's no reason the service won't still be running without a connection.
also this is not about netowkring, but about a server. moved to Linux - Server.