我已经处理过BIND多年了,这总是让我感到烦恼.
$dig google.com ns ;; QUESTION SECTION: ;google.com. IN NS ;; ANSWER SECTION: google.com. 87046 IN NS ns3.google.com. etc... ;; ADDITIONAL SECTION: ns1.google.com. 87274 IN A 216.239.32.10 etc.
我知道,至少在概念上,根服务器处理.并将.com.,..gov.交给任何正确的服务器(尽管在实践中这都被缓存了几个级别),但在某些时候,有人有要知道在216.239.32.10向服务器询问whatever.google.com的A记录.但是,首先,解析器是如何解决这个问题的,因为你需要知道NS的A来做到这一点？ (就此而言,既然我们知道它是一个互联网NS,而不是混乱之类的东西,为什么你必须使用一个名字而不是NS记录的地址？)
我的名字服务器总是有上游某人可以找到的名字(例如,我在foo.com上为bar.com托管了DNS,我的上游处理了foo.com),但我从来没有完全理解像Google这样的人如何克服以google.com的名义为google.com托管DNS的鸡和蛋问题.
解决方法
For example,if the authoritative name server for example.org is ns1.example.org,a computer trying to resolve www.example.org first resolves ns1.example.org. Since ns1 is contained in example.org,this requires resolving example.org first,which presents a circular dependency. To break the dependency,the name server for the top level domain org includes glue along with the delegation for example.org. The glue records are address records that provide IP addresses for ns1.example.org. The resolver uses one or more of these IP addresses to query one of the domain’s authoritative servers,which allows it to complete the DNS query.
