所謂四層就是基于IP+端口的負(fù)載均衡，通過虛擬IP+端口接收請(qǐng)求，然后再分配到真實(shí)的服務(wù)器；七層通過虛擬的URL或主機(jī)名接收請(qǐng)求，然后再分配到真實(shí)的服務(wù)器七層就是基于URL等應(yīng)用層信息的負(fù)載均衡。

七層負(fù)載：

[root@www ~]# cat /etc/nginx/conf.d/test.conf
upstream phpserver {
        server192.168.2.3;
        server192.168.2.4;
        }
upstream htmlserver {
server192.168.2.1;
       server192.168.2.2;
       }
[root@www ~]# vim /etc/nginx/nginx.conf
      location / {
root  /usr/share/nginx/html;
            index  index.html index.htm;
         if ($request_uri ~*\.html$){
                       proxy_pass http://htmlserver;
                }
            if ($request_uri~* \.php$){
                       proxy_pass http://phpserver;
                }
        }

四層負(fù)載：

[root@linux-node1 conf]# vim nginx.conf         
worker_processes  1;
events {
    worker_connections  1024;
}
stream {  #類似于7層的http段
        upstream ssh_proxy {
        hash $remote_addr consistent;
        server 192.168.56.2:22;
        server 192.168.56.3:22;
   }
      server {
        listen 2222;
        proxy_connect_timeout 1s;
        proxy_timeout 3s;
        proxy_pass ssh_proxy;
     }
  }