今天wget一个网站时，发现很慢：
1 # wget www.baidu.com 2 --2017-05-29 12:29:49-- http://www.baidu.com/ 3 Resolving www.baidu.com... 14.215.177.38, 14.215.177.37 ##此处停顿约5秒 4 Connecting to www.baidu.com|14.215.177.38|:80... connected. 5 HTTP request sent, awaiting response... 200 OK 6 Length: 2381 (2.3K) [text/html] 7 Saving to: “index.html.1” 8 9 100%[============================================>] 2,381 --.-K/s in 0s 10 11 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
1 [root@web02 scripts]# wget -4 www.baidu.com 2 --2017-05-29 12:31:59-- http://www.baidu.com/ 3 Resolving www.baidu.com... 14.215.177.38, 14.215.177.37 4 Connecting to www.baidu.com|14.215.177.38|:80... connected. 5 HTTP request sent, awaiting response... 200 OK 6 Length: 2381 (2.3K) [text/html] 7 Saving to: “index.html.2” 8 9 100%[============================================>] 2,381 --.-K/s in 0s 10 11 2017-05-29 12:31:59 (96.3 MB/s) - “index.html.2” saved [2381/2381]
瞬间完成
原文：http://www.cnblogs.com/ginvip/p/6917768.html