wget一个网站很慢的原因

今天wget一个网站时，发现很慢：

# wget www.baidu.com
--2017-05-29 12:29:49--  http://www.baidu.com/
Resolving www.baidu.com... 14.215.177.38, 14.215.177.37  ##此处停顿约5秒
Connecting to www.baidu.com|14.215.177.38|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2381 (2.3K) [text/html]
Saving to: “index.html.1”

100%[============================================>] 2,381       --.-K/s   in 0s      

2017-05-29 12:29:54 (108 MB/s) - “index.html.1” saved [2381/2381]

默认会优先解析 IPv6，在那个 domain 没有 IPv6 的情况下，会等待 IPv6 解析失败 timeout 之后才按以前的正常流程去找 IPv4

[root@web02 scripts]# wget -4 www.baidu.com
--2017-05-29 12:31:59--  http://www.baidu.com/
Resolving www.baidu.com... 14.215.177.38, 14.215.177.37
Connecting to www.baidu.com|14.215.177.38|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2381 (2.3K) [text/html]
Saving to: “index.html.2”

100%[============================================>] 2,381       --.-K/s   in 0s      

2017-05-29 12:31:59 (96.3 MB/s) - “index.html.2” saved [2381/2381]

瞬间完成