这个主域名如何拥有CNAMElogging？

我的印象是只有子域名可以拥有CNAMElogging：主域名需要定义他们自己的logging。但是， apt-get.com似乎只有一个CNAMElogging。这怎么能工作？

 $ dig apt-get.com ; <<>> DiG 9.8.1-P1 <<>> apt-get.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45743 ;; flags: qr rd ra; QUERY: 1, ANSWER: 9, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;apt-get.com. IN A ;; ANSWER SECTION: apt-get.com. 86336 IN CNAME thie5ku9.dsgeneration.com. thie5ku9.dsgeneration.com. 60 IN A 208.73.211.242 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.246 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.166 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.232 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.161 thie5ku9.dsgeneration.com. 60 IN A 208.73.210.233 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.186 thie5ku9.dsgeneration.com. 60 IN A 208.73.211.188 ;; Query time: 59 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Tue Jun 10 15:05:48 2014 ;; MSG SIZE rcvd: 193 $ dig apt-get.com ns ; <<>> DiG 9.8.1-P1 <<>> apt-get.com ns ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 43831 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;apt-get.com. IN NS ;; Query time: 26 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Tue Jun 10 15:12:37 2014 ;; MSG SIZE rcvd: 29 $ dig apt-get.com ns @b.gtld-servers.net ; <<>> DiG 9.8.1-P1 <<>> apt-get.com ns @b.gtld-servers.net ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 38228 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 2 ;; WARNING: recursion requested but not available ;; QUESTION SECTION: ;apt-get.com. IN NS ;; AUTHORITY SECTION: apt-get.com. 172800 IN NS ns1.domainrecover.com. apt-get.com. 172800 IN NS ns2.domainrecover.com. ;; ADDITIONAL SECTION: ns1.domainrecover.com. 172800 IN A 66.45.232.66 ns2.domainrecover.com. 172800 IN A 65.23.159.179 ;; Query time: 70 msec ;; SERVER: 192.33.14.30#53(192.33.14.30) ;; WHEN: Tue Jun 10 15:07:05 2014 ;; MSG SIZE rcvd: 111

该域名确实解决。我得到以下标题：

 GET / HTTP/1.1 User-Agent: Testing_Sniffer/4.15 Host: apt-get.com Accept: */* HTTP/1.0 200 (OK) Cache-Control: private, no-cache, must-revalidate Connection: Keep-Alive Pragma: no-cache Server: Oversee Turing v1.0.0 Content-Length: 1347 Content-Type: text/html Expires: Mon, 26 Jul 1997 05:00:00 GMT Keep-Alive: timeout=3, max=96 P3P: policyref="http://www.dsparking.com/w3c/p3p.xml", CP="NOI DSP COR ADMa OUR NOR STA" Set-Cookie: parkinglot=1; domain=.apt-get.com; path=/; expires=Wed, 11-Jun-2014 14:10:37 GMT

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd"> <!-- turing_cluster_prod --> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>apt-get.com</title> <meta name="keywords" content="apt-get.com" /> <meta name="description" content="apt-get.com" /> <meta name="robots" content="index, follow" /> <meta name="revisit-after" content="10" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <script type="text/javascript"> document.cookie = "jsc=1"; </script> </head> <frameset rows="100%,*" frameborder="no" border="0" framespacing="0"> <frame src="http://apt-get.com?epl=5PfLSSqWrYDAt-gbwMDK_rA3b1UJCYVTJHfxTzr9FTDQV84b6vAgVhU3FTeCRQNiuRNv79Ni0V3mkEVNRhpqo2gpMjp5iOIR1w2_EISPENaqzoXohVXl2QI3ryXlRCB4FaIIaxynnWXWY6QBgBgNiIZ6agD1NBoNGg0ajXpUCXUAIJDer78AAOB_AwAAQIDbCwAAe_NWlVlTJllBMTZoWkKPAAAA8A" name="apt-get.com"> </frameset> <noframes> <body><a href="http://apt-get.com?epl=5PfLSSqWrYDAt-gbwMDK_rA3b1UJCYVTJHfxTzr9FTDQV84b6vAgVhU3FTeCRQNiuRNv79Ni0V3mkEVNRhpqo2gpMjp5iOIR1w2_EISPENaqzoXohVXl2QI3ryXlRCB4FaIIaxynnWXWY6QBgBgNiIZ6agD1NBoNGg0ajXpUCXUAIJDer78AAOB_AwAAQIDbCwAAe_NWlVlTJllBMTZoWkKPAAAA8A">Click here to go to apt-get.com</a>.</body> </noframes> </html>

你误解了RFC的性质。任何人都可以自由地违反他们，但可能会导致不可预知的行为。你可以看到一个很好的例子：当你从.com服务器请求域名的NSlogging时，你会得到一个答案（一对logging），但是当你通过正常的recursion来做时，你会得到一个不同的结果SERVFAIL ）。

正如你所期望的那样，域名的parsing是有效的（毕竟有一个CNAME），但是以可靠的方式做域名（无邮件，无www.服务器）是非常困难的。

你已经发布了一个完美的例子，说明为什么违反RFC是不明智的。

这实际上是CNAME的有效使用。您可以在DNS区域的顶点上使用CNAME，但不能将其与任何其他loggingtypes（如MX）一起使用。对于大多数域名所有者来说，这是一个令人无法接受的折衷scheme，但是它会不时被使用。