【为啥使用 ping 到的 IP 不能访问的网站，而百度就可以】

■网友
$ dig http://zhihu.com +short
118.89.204.192
118.89.204.190

$ curl -IL http://118.89.204.192 -H \u0026#39;Host:zhihu.com\u0026#39;
HTTP/1.1 301 Moved Permanently
Date: Tue, 30 Apr 2019 02:31:08 GMT
Content-Type: text/html
Content-Length: 182
Connection: keep-alive
Set-Cookie: tgw_l7_route=a37704a413efa26cf3f23813004f1a3b; Expires=Tue, 30-Apr-2019 02:46:08 GMT; Path=/
Location: https://www.zhihu.com/
X-Backend-Response: 0.000
Server: ZWS
Vary: Accept-Encoding

就这么简单个事……

■网友
做了一个实验：1. 首先使用dns解析下http://www.zhihu.com的ip地址
$ nslookup www.zhihu.comServer:\t\t114.114.114.114Address:\t114.114.114.114#53Non-authoritative answer:www.zhihu.com\tcanonical name = planets-cats.zhihu.com.planets-cats.zhihu.com\tcanonical name = solarflare03.zhihu.com.solarflare03.zhihu.com\tcanonical name = k7itxdrj.gsadds.com.Name:\tk7itxdrj.gsadds.comAddress: 118.89.204.190Name:\tk7itxdrj.gsadds.comAddress: 118.89.204.192可以看到解析到两个ip，一个是 118.89.204.190，一个是118.89.204.192，两者等价，接下来的实验中，使用的是118.89.204.190这个ip。
2. 直接访问dns系统解析到的ip地址。
2.1 使用http访问 http://118.89.204.190使用的是http协议，主机118.89.204.190上80端口的应用服务器在应用层拒绝了直接通过ip访问的请求。原因是返回了一个html页面，所以这个请求是一个在应用层处理的请求，处理的逻辑是简单的拒绝了。（说句题外话，我推荐使用重定向）
2.2 使用https进行访问https://118.89.204.190首先浏览器会警告这个ip地址的证书有问题，需要手动添加到信任ip，接着443端口的服务器也在应用层拒绝了请求
请求：
请求网址：https://118.89.204.192/GET / HTTP/1.1Host: 118.89.204.192User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:66.0) Gecko/20100101 Firefox/66.0Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2Accept-Encoding: gzip, deflate, brConnection: keep-aliveCookie: _zap=af8e0c0c-435b-483c-ab4d-fb86ca8e6020; d_c0="AKAjpcslDg-PTuwgw-S-BSlU8YrYwjf9w64=|1551427469"; _xsrf=asOXc1EYwWCKRRPBSJoKqtK04fOfM8uz; capsion_ticket="2|1:0|10:1556453804|14:capsion_ticket|44:MDk4ODkxMWRiNTBlNDIwZmEwNTEzZjEzMjE5MTE0MzE=|ac1435b4f3b476d99007334812e038c58280c2d7de03e1827a1fba2d4c3b2799"; r_cap_id="MjljMGVlNGU0ZDY5NDdkZTk2NjFiNzZiMTRkYjZiNTc=|1556453807|d3f0afd0b437c15a58c4de27ef4cc78b307424d4"; cap_id="Y2Q4MmZlOTgxMDMwNGExYmI0Mzc5OGJiODQyY2JjNmY=|1556453807|5176a3d85806ac3c6f9c8d9104ad6029c4575d69"; l_cap_id="MzZkNWQzNGViMjBkNGM0OGFjMDNkMTA5NTQ3ODcwMDQ=|1556453807|7864c71feebc6ee83596297404c115b19eec037d"; z_c0=Mi4xYXdLTEFnQUFBQUFBb0NPbHl5VU9EeGNBQUFCaEFsVk52dWV5WFFDbzEyQ0llT1dnMEY3UDFEUExmYldWMTUxSHRB|1556453822|a054a74c7d0cb75a88dceec93da46746143c32de; tst=r; q_c1=5271c2958b1c412fa9a9e0b5b50604c9|1556453828000|1556453828000; __gads=ID=2d9cb482a8f15c3e:T=1556453831:S=ALNI_MZXP7BURulhpZ0JBDM1NOcuzdDVkg; tgw_l7_route=66cb16bc7f45da64562a077714739c11Upgrade-Insecure-Requests: 1Cache-Control: max-age=0, no-cacheTE: TrailersPragma: no-cache