关于Win7中的host文件改动

以下是摘自 http://serverfault.com/questions/4689/windows-7-localhost-name-resolution-is-handled-within-dns-itself-why 的关于解答win7中host文件改动原因的解答：

Q:
After 18 years of hosts files on Windows, I was surprised to see this in Windows 7 build 7100:

# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost

Does anyone know why this change was introduced? I'm sure there has to be some kind reasoning.

A:
I checked with a developer on the Windows team, and the actual answer is much more innocuous than the other answers to this post :)

At some point in the future, as the world transitions from IPV4 to IPV6, IPV4 will be eventually be disabled/uninstalled by companies that want to simplfy network management in their environments.

With Windows Vista, when IPv4 was uninstalled and IPv6 was enabled, a DNS query for an A (IPv4) address resulted in the IPv4 loopback (which came from the hosts file). This of course caused problems when IPv4 was not installed. The fix was to move the always present IPv4 and IPv6 loopback entries from the host into the DNS resolver, where they could be independently disabled.