Question

是ip一对一映射的主机名吗？主机名如何有多个IP地址？根据Java的getAllByName，它返回一个hostName的ips列表，但是它的文档似乎暗示或者至少没有解释一对多的映射：

The host name can either be a machine name, such as "java.sun.com", or a textual representation of its IP address.

http://download.oracle.com/javase/1.4.2/docs/api/java/net/InetAddress.html#getAllByName%28java.lang.String%29

Answer 1

不，每个主机名都可以有多个指向不同IP的DNS A记录。这通常用于高级负载平衡。例如，您可以在google.com：

上查看

$ host google.com
google.com has address 209.85.148.104
google.com has address 209.85.148.105
google.com has address 209.85.148.103
google.com has address 209.85.148.106
google.com has address 209.85.148.147
google.com has address 209.85.148.99
google.com mail is handled by 30 alt2.aspmx.l.google.com.
google.com mail is handled by 20 alt1.aspmx.l.google.com.
google.com mail is handled by 50 alt4.aspmx.l.google.com.
google.com mail is handled by 40 alt3.aspmx.l.google.com.
google.com mail is handled by 10 aspmx.l.google.com.

Answer 2

实际上，机器的IP取决于该盒子所用的网络接口卡（NIC）的数量。因此，如果一台机器安装了3个NIC，则该机箱将有1个主机名，但有3个不同的IP。

Answer 3

不，主机名可能有多个A记录，在这种情况下，解析器会将所有IP地址作为列表返回。您几乎可以在每个大型网站上查看它：

;; QUESTION SECTION:
;google.com.                    IN      A

;; ANSWER SECTION:
google.com.             283     IN      A       74.125.232.82
google.com.             283     IN      A       74.125.232.81
google.com.             283     IN      A       74.125.232.83
google.com.             283     IN      A       74.125.232.80
google.com.             283     IN      A       74.125.232.84

ip是一对一映射的主机名吗？

3 个答案: