C:\Documents and Settings\zhangc>nslookup
DNS request timed out.
timeout was 2 seconds.
*** Can't find server name for address 172.16.77.6: Timed out
*** Default servers are not available
Default Server: UnKnown
Address: 172.16.77.6
原因：DNS客户机默认DNS服务器填写不正确或没有填写，应检查客户机DNS指向是否正确
C:\Documents and Settings\zhangc>nslookup asd.zc.com.cn
Server: dns.zc.com.cn
Address: 172.16.77.77
*** dns.zc.com.cn can't find asd.zc.com.cn: Non-existent domain
原因：DNS服务器中没有这条记录（无法找到要解析的记录），应检查A记录在创建时主机名是否正确
C:\Documents and Settings\zhangc>nslookup www.wnt.com.cn
Server: dns.zc.com.cn
Address: 172.16.77.77
DNS request timed out.
timeout was 2 seconds.
DNS request timed out.
timeout was 2 seconds.
*** Request to dns.zc.com.cn timed-out
原因：客户机向DNS服务器解析了一个非DNS服务器所管辖区域的域名，所以DNS服务器应采取寻树或转发的方式帮助客户机解析域名，返回这种结果代表服务器无法联系到其他的DNS服务器（无法寻树或向转发服务器发送请求），应检查服务器网络连通性。
C:\Documents and Settings\zhangc>nslookup
*** Can't find server name for address 172.16.77.77: Non-existent domain
*** Default servers are not available
Default Server: UnKnown
Address: 172.16.77.77
原因：DNS服务器PTR记录错误或没有创建
C:\Documents and Settings\zhangc>nslookup
DNS request timed out.
timeout was 2 seconds.
*** Can't find server name for address 172.16.77.77: Timed out
*** Default servers are not available
Default Server: UnKnown
Address: 172.16.77.77
原因：DNS服务器反向区域错误或没有创建
> 172.16.77.11
Server: dns.zc.com.cn
Address: 172.16.77.77
*** dns.zc.com.cn can't find 172.16.77.11: Non-existent domain
原因：服务器无法找到这条记录（PTR）
