apache 反向代理 iis 502 proxy error:配置报错 

最近服务器发生一怪事  之前搭建环境时  用apache反向代理 iis时是处理过这个问题的 

Proxy Error

The proxy server received an invalid response from an upstream server. The proxy server could not handle the request GET /.

Reason: DNS lookup failure for: hehe.amd2015.com

当时也是按照网上的方法在我的vhosts.conf内直接加入了

ProxyRequests Off <Proxy *> Order deny,allow Allow from all </Proxy>

SetEnv force-proxy-request-1.0.1

SetEnv proxy-nokeepalive 1

然后服务器正常运行了数月，直到前两天又莫名出现了这个问题，
eg：下面这个二级域名的配置

<VirtualHost *:80> ServerAdmin Snooker.amd2015.com DocumentRoot "X:\XXXXX\XXXX\wwwroot" ServerName Snooker.amd2015.com ProxyPass / http://Snooker.amd2015.com:81/ ProxyPassReverse / http://Snooker.amd2015.com:81/ ErrorLog "logs/Snooker.amd2015.com-error.log" CustomLog "logs/Snooker.amd2015.com-access.log" common SetEnv force-proxy-request-1.0.1 SetEnv proxy-nokeepalive 1 </VirtualHost>

但是这次奇怪的就在如果配置的是正式域名的就能正常访问，
eg：

<VirtualHost *:80> ServerAdmin www.jyzsjj.com DocumentRoot "X:\XXXXX\XXXX\wwwroot" ServerName www.jyzsjj.com ProxyPass / http://www.jyzsjj.com:81/ ProxyPassReverse / http://www.jyzsjj.com:81/ ErrorLog "logs/jyzs.amd2015.com-error.log" CustomLog "logs/jyzs.amd2015.com-access.log" common SetEnv force-proxy-request-1.0.1 SetEnv proxy-nokeepalive 1 </VirtualHost>

这里是error.log:

[Fri May 22 13:48:48.504381 2015] [proxy:error] [pid 7428:tid 2864] [client xxx.xxx.xxx.xxx:xxx] AH00898: DNS lookup failure for: snooker.amd2015.com returned by / [Fri May 22 13:48:48.555159 2015] [proxy:error] [pid 7428:tid 2864] [client xxx.xxx.xxx.xxx:xxx] AH00898: DNS lookup failure for: snooker.amd2015.com returned by /favicon.ico, referer: http://snooker.amd2015.com/