If that works, it just gives the mappings in that zone, and the zone does not necessarily have any relationship to network addressing. That is, it'll give you all of yahoo.com, but the hosts in yahoo.com might be 192.168.4.45 and 10.78.4.123. In addition, there may well be computers in those subnets that exist in DNS and aren't in yahoo.com. To extend the above example, there may be a computer at 192.168.4.46 whose FQDN is www.yimg.com.