If a secondary name server can't get the current serial number for a zone from its master server, you won't be warned about it initially. However, if the problem persists and the secondary can't determine within the expire interval whether or not its data is up to date, it expires the zone. On a Microsoft DNS Server, you'll see a message like this in the DNS Server event log:
Zone movie.edu expired before it could obtain a successful zone transfer or update from a master server acting as its source for the zone. The zone has been shut down.
Once the zone has expired and the name server has shut it down, you'll start getting Query refused errors when you query the name server for data in the zone:
nslookup robocop wormhole.movie.edu.Server: wormhole.movie.edu Addresses: 22.214.171.124, 126.96.36.199 *** wormhole.movie.edu can't find robocop.movie.edu: Query refused
Three leading causes of this problem are a loss in connectivity to the master server due to network failure, an incorrect IP address configured for the master server, and a syntax error in the zone datafile on the master server.
First, use the DNS console to check the address of the master server(s) from which the secondary is attempting to load data. Right-click the domain name of the zone in the left pane, choose Properties, and look at the General tab, shown in Figure 15-3.
Figure 15-3. Zone properties window showing master server(s)
Make sure that's really the IP address ...