原理
首先有一个虚拟ip暴露给客户端，虚拟ip对应的mac地址为一台真实服务器，即用户向虚拟ip发送一个请求，该请求会被分发到真实服务器上。
现在有2台真实服务器，一台master，一台backup，master和backup上都运行着keepalived，当master挂了的时候，backup检测之后，自己成为master,且arp缓存虚拟ip对应的mac地址将变为backup的mac地址，这样请求虚拟ip的报文会被发送到backup
架构图如下：
安装
主机：192.168.1.227
备机：192.168.1.246
虚拟ip：192.168.1.99
安装命令：
wget http://www.keepalived.org/software/keepalived-1.2.13.tar.gz
tar -zxvf keepalived-1.2.13.tar.gz
cd keepalived-1.2.13
./configure --disable-fwmark --prefix=/usr/local/keepalived
make && make install
整理：
mkdir /etc/keepalived/
cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
ln -s /usr/local/keepalived/sbin/keepalived /sbin/
配置：
vi /etc/keepalived/keepalived.conf
Master
! Configuration File for keepalived
global_defs {
notification_email {
[email protected]
[email protected]
[email protected]
}
notification_email_from [email protected]
smtp_server 192.168.200.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.99
}
}
Backup 和master一样，只要修改如下地方：
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 51
priority 99 # 这里改为99，master优先级是100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.99
}
}
管理命令：
停止
service keepalived stop
启动
service keepalived start
重启
service keepalived restart
查看状态
service keepalived status
测试
在本机上查看虚拟ip状态
ip add
在同一网段的其他机器上查询arp缓存
arp -a
这里的1.99对应的mac地址是1.227
停掉master的keepalived
service keepalived stop
在同一网段的其他机器上查询arp缓存
arp –a
发现1.99的mac地址已经变为slave的mac地址
那么主备双机热备就完成了
总结：本篇文章实现的功能
1.master主机挂了，或者master 上keepalived挂了之后，可以切换到slave
2.master的网络不通的时候，可以立即切换到slave，但是如果只是master上的应用出现问题的时候，是不会主动切换的，这个要通过编写脚本来监控应用出问题，这个问题后续再讨论吧。