通过代理发送curl请求时出错\u DNS\u失败

当我使用我的代理对google/facebook等一般网站进行卷曲时，它工作得很好。但是当我尝试卷曲一个应该可用的内部主机时，我得到以下消息：

<div id="content">
<p>The following error was encountered while trying to retrieve the URL: <a href="http://x.yz.com/">http://x.yz.com/</a></p>

<blockquote id="error">
<p><b>Unable to determine IP address from host name <q>x.yz.com</q></b></p>
</blockquote>

<p>The DNS server returned:</p>
<blockquote id="data">
<pre>Name Error: The domain name does not exist.</pre>
</blockquote>

<p>This means that the cache was not able to resolve the hostname presented in the URL. Check if the address is correct.</p>

<p>Your cache administrator is <a href="mailto:webmaster?subject=CacheErrorInfo%20-%20ERR_DNS_FAIL&amp;body=CacheHost%3A%20538a0f427a73%0D%0AErrPage%3A%20ERR_DNS_FAIL%0D%0AErr%3A%20%5Bnone%5D%0D%0ADNS%20ErrMsg%3A%20Name%20Error%3A%20The%20domain%20name%20does%20not%20exist.%0D%0ATimeStamp%3A%20Tue,%2007%20Nov%202017%2022%3A18%3A35%20GMT%0D%0A%0D%0AClientIP%3A%20192.168.99.1%0D%0A%0D%0AHTTP%20Request%3A%0D%0AGET%20%2F%20HTTP%2F1.1%0AUser-Agent%3A%20curl%2F7.43.0%0D%0AAccept%3A%20*%2F*%0D%0AProxy-Connection%3A%20Keep-Alive%0D%0AHost%3A%x.yz.com%0D%0A%0D%0A%0D%0A">webmaster</a>.</p>
<br>
</div>

<hr>
<div id="footer">
<p>Generated Tue, 07 Nov 2017 22:18:35 GMT by 538a0f427a73 (squid/3.5.12)</p>
<!-- ERR_DNS_FAIL -->
</div>

尝试检索URL时遇到以下错误：

无法从主机名x.yz.com确定IP地址

DNS服务器返回：

名称错误：域名不存在。
这意味着缓存无法解析URL中显示的主机名。检查地址是否正确

您的缓存管理员是




由538a0f427a73（squid/3.5.12）于2017年11月7日星期二22:18:35 GMT生成

在设置所述主机的同一虚拟机中设置代理。我应该调查什么？谢谢