使用nslookup会出现Cannot find servername for address172.16.0.4:Non-existent domain，DefaultServer:Unknown

网络中心建立了一个内网dns服务器，其地址是172.16.0.4，负责在内部解析域名，设置web服务器内网ip为172.16.0.4，在tyut.edu.cn上申请了域名qfmy.tyut.educ.cn，并指向网通分配的外网地址218.26.207.118,，在客户机tcp/ip中设置首选dns172.16.0.4,备用dns202.99.192.68

现象是：有时候在浏览器客户端无法访问学院网站，但是修复一下客户端的网络连接或者重新启动一下服务器就能访问，临时的解决办法我在前面也谈过，另外，当打不开网站时浏览器试图连接外网地址。

why?

CannotfindServernameforaddress的另外一种可能：

IfyougointotheNSLOOKUPprogramanditimmediatelygivesyouanerrormessagesomethingalongthelinesof:
--------------------------------------------------
***Can'tfindServernameforaddress...
Non-existentdomain
***Defaultserversarenotavailable
DefaultServer:Unknown
--------------------------------------------------

Youareexperiencingacommonproblemcausedbyanimproperlyconfiguredreversearpa(in-addr.arpa)zone.

WhentheNSLOOKUPprogramstartsitgoestotheTCP/IPconfigurationforthesystemonwhichitisrunning.FromtheconfigurationitdeterminestheIPaddressoftheDNSserverthatthesystemisconfiguredtouse.TheNSLOOKUPdoesareverselookupusingtheIPaddressoftheDNSserverandtriestodeterminethenameoftheserver.

IfthereversearpazoneforthatIPaddressisnotsetupcorrectly,thenNSLOOKUPcannotdeterminethenameassociatedwiththatIPaddress,anditdisplaystheerrormessagegivenabove.

TofixthisproblemyouneedtoproperlyconfigurethereversearpazonefortheIPaddressoftheDNSserver,andmakesurethatthereversearpaisproperlydelegatedtotheserver.

仍没有解决，郁闷阿!