keepalived是一个类似于layer3, 4 & 7交换机制的软件，也就是我们平时说的第3层、第4层和第7层交换。Keepalived是自动完成，不需人工干涉。
调度服务器：
需要在LVS的基础上面做。
参考上两节：
负载均衡群集之一LVS-DR：https://blog.51cto.com/13572519/2084197
负载均衡群集之—LVS-NAT：https://blog.51cto.com/13572519/2084181

一块网卡：
Vmnet1：192.168.80.100
主与从调度器上都做下面的3步的：加载、安装ipvsadm包
下载地址：http://www.keepalived.org/download.html
[root@lss ~]# modprobe ip_vs
[root@lss ~]# rpm -ivh /mnt/Packages/ipvsadm-1.27-7.el7.x86_64.rpm
---------keepalived安装配置（主、从都要配置的）----
[root@lss ~]# yum -y install popt-devel kernel-devel openssl-devel
WinSCP上传keepalived到主从服务器

[root@lss ~]# tar fx keepalived-1.4.2.tar.gz -C /opt
[root@lss opt]# cd /opt/keepalived-1.4.2/
[root@lss keepalived-1.4.2]# yum -y install \
gcc \
gcc-c++ \
make
[root@lss keepalived-1.4.2]# ./configure --prefix=/
[root@lss keepalived-1.4.2]# make && make install
[root@lss keepalived]# cp -r /opt/keepalived-1.4.2/keepalived/etc/keepalived/ /etc/init.d
[root@lss keepalived]# systemctl enable keepalived
--------------------------------修改配置文件（主调度器）-------------
[root@lss keepalived]# vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {acassen@firewall.loc
br/>sysadmin@firewall.loc
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 192.168.200.1
smtp_connect_timeout 30
router_id LVS_01
}

vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 110
advert_int 1
authentication {
auth_type PASS
auth_pass 6666
}
virtual_ipaddress {
192.168.80.188
}
}
virtual_server 192.168.80.188 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 60
protocol TCP
real_server 192.168.80.101 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 192.168.80.102 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
[root@lss keepalived]# service keepalived start
[root@lss keepalived]# ip addr show dev ens33     //验证绑定了虚拟地址
inet 192.168.80.188/32 scope global ens33
[root@lss keepalived]# ipvsadm -L
[root@lss keepalived]# tail -f /var/log/messages   //对业务服务器和主调度器进行关闭验证热备及健康检查效果。
MASTER STATE代表主服务器
BACKUP STATE代表备用服务器

---------------------------------修改配置文件（从调度器）-----------------
[root@LSS03 ~]# modprobe ip_vs
[root@LSS03 ~]# rpm -ivh /mnt/Packages/ipvsadm-1.27-7.el7.x86_64.rpm
[root@LSS03 ~]# yum -y install \
gcc \
gcc-c++ \
make
[root@LSS03 ~]# tar fx keepalived-1.4.2.tar.gz -C /opt
[root@LSS03 ~]# cd /opt/keepalived-1.4.2/
[root@LSS03 keepalived-1.4.2]# ./configure --prefix=/
[root@LSS03 keepalived-1.4.2]# make && make install
[root@LSS03 keepalived-1.4.2]# cp -r keepalived/etc/init.d/keepalived /etc/init.d/
[root@LSS03 keepalived-1.4.2]# systemctl enable keepalived
[root@LSS03 keepalived-1.4.2]# vi /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
notification_email {
root@localhost.localdomain
}
notification_email_from benet root@localhost.localdomain
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_02       //主从要不相同
}

vrrp_instance VI_1 {
state BACKUP        //从调度器的热备状态
interface ens33
virtual_router_id 51    //编号主与从的两边要一样的
priority 105    //从调度器的优先级
advert_int 1
authentication {    //主、从热备认证信息
auth_type PASS
auth_pass 6666
}
virtual_ipaddress {     //指定群集VIP地址（虚拟服务器地址），可以指定多个的    
192.168.80.188
}
}

virtual_server 192.168.80.188 80 {      //虚拟服务器地址（VIP）、端口
delay_loop 6       //健康检查的间隔时间（秒）正常情况下。
lb_algo rr       //轮询（rr）调度算法
lb_kind DR         //直接路由（DR）群集工作模式
persistence_timeout 60     //连接保持时间，（秒），若注释掉加个"!"在这个时间内同一客户端的请求被同一服务器处理
protocol TCP       //应用服务采用的是TCP协议

real_server 192.168.80.101 80 { //第一个web节点的地址、端口      
weight 1    //节点的权重
TCP_CHECK {             //健康检查方式
connect_port 80                //检查的目标端口
connect_timeout 3  //连接超时（秒）
nb_get_retry 3         //重试次数
delay_before_retry 3   //重试间隔（秒）
}
}
real_server 192.168.80.102 80 { //第二个web节点的地址、端口
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
[root@LSS03 keepalived-1.4.2]# service keepalived start
[root@LSS03 keepalived-1.4.2]# ip addr show dev ens33
[root@LSS03 keepalived-1.4.2]# tail -f /var/log/messages
MASTER STATE代表主服务器
BACKUP STATE代表备用服务器

以下是WEB服务器：
192.168.80.101服务器：
[root@lss01 ~]# yum install -y httpd
[root@lss01 ~]# vi /etc/httpd/conf/httpd.confServerName www.aa.com
[root@lss01 ~]# vi /var/www/html/index.html

Server aa

192.168.80.102服务器：
[root@lss02 ~]# yum install -y httpd
[root@lss02 ~]# vi /etc/httpd/conf/httpd.conf
ServerName www.bb.com
[root@lss02 ~]# vi /var/www/html/index.html

Server bb