在Linux Router Backup上安装keepalived的方法是相同的，不同的是配置文件/usr/local/keepalived/etc/keepalived/keepalived.conf，如下：
vrrp_instance VI_1 {
state BACKUP
interface eth1
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.3.3
}
}
在启动Master上的keepalived之前，我们先看一下Master上eth1的情况：
# ip add show eth1
8: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:e0:4c:3a:d7:25 brd ff:ff:ff:ff:ff:ff
inet 192.168.3.1/24 brd 192.168.3.255 scope global eth1
inet6 fe80::2e0:4cff:fe3a:d725/64 scope link
我们看到只有一个IP地址：192.168.3.1/24，现在我们启动Master上的keepalived：
#/usr/local/keepalived/sbin/keepalived –D –
f /usr/local/keepalived/etc/keepalived/keepalived.conf
现在我们再看一下Master上eth1的情况：
# ip add show eth1
8: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
link/ether 00:e0:4c:3a:d7:25 brd ff:ff:ff:ff:ff:ff
inet 192.168.3.1/24 brd 192.168.3.255 scope global eth1
inet 192.168.3.3/32 scope global eth1
inet6 fe80::2e0:4cff:fe3a:d725/64 scope link
我们看到有两个IP地址，其中一个就是V-Gate:192.168.3.3/32
用同样的方法启动Backup上的keepalived：
#/usr/local/keepalived/sbin/keepalived –D –
f /usr/local/keepalived/etc/keepalived/keepalived.conf
这样，当Master失效时，Backup就会通过MultiCast地址：224.0.0.18这个组播地址，获得这个消息，并将192.168.3.3这个地址接管过来。
总结，请你注意一下我们这个实验的题目“利用Keepalived的VRRP功能实现简单的路由器备份”，而不是路由备份。我们这个实验的目的，是让大家熟悉VRRP协议和如何利用Keepalived实现VRRP协议。
