keepalived+nginx+httpd搭建高可用服务器，避免单点故障

环境准备：服务器1:192.168.2.121,nginx+keepalived服务器2:192.168.2.122,nginx+keepalived服务器3:192.168.2.123,httpd服务器4:192.168.2.124,httpdvip：192.168.2.881、keepalive