双机热备经典案例之Cisco HSRP的配置
HSRP一般用于两台，也可以用于多台 。必须在每台起HSRP上的路由器上配置 。
When the HSRP is configured on a network segment, it provides a virtual Media Access Control (MAC) address and an IP address that is shared among routers in a groupof routers that is running HSRP. One of these devices is selected by the protocol to be the active router. The active router receives and routes packets destined for the group"s MAC address. For n routers running HSRP, there are n1 IP and MAC addresses assigned.
但是aceive只有一台，standby只有一台，其实其他的都在监听状态 。所以zyx说的是处在active和standby的状态的只有两台 。
附一个配置实例：
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname r1
!
enable password cisco
!
ip subnet-zero (新版的IOS都支持全0/1子网)
!
!
!
!
interface Ethernet0
ip address 136.147.107.101 255.255.0.0
no ip redirects
no ip directed-broadcast
standby 150 timers 5 15;;;/* 定义150组5秒交换一次hello信息，15秒没收到;hello信息就开始切换 */
standby 150 priority 110 /* 定义150组的主路由器权值，值越大，为主路由器希望越大 */
standby 150 preempt /* enable 150组的hsrp抢占功能 */
standby 150 authentication cisco;;/* 设置150组的router身份验证串 */
standby 150 ip 136.147.107.100 /* 定义150组的浮动地址，也是这台router
连接的网络的网关 */
standby 150 track Ethernet0 /* 定义监控的端口 */
!
interface Serial0
no ip address
no ip directed-broadcast
no ip mroute-cache
shutdown
no fair-queue
!
ip classless
!
!
line con 0
transport input none
line 1 16
line aux 0
line vty 0 4
password cisco
login
!
end
配置基本HSRP例子：
提问 "当主用路由器当掉以后备份路由器可以接管主用路由器的IP地址和MAC地址
回答
Router1：
Router1#configure terminal
Enter configuration commands, one per line.;End with CNTL/Z.
Router1(config)#interface FastEthernet 0/1
Router1(config-if)#ip address 172.22.1.3 255.255.255.0
Router1(config-if)#standby 1 ip 172.22.1.1
Router1(config-if)#standby 1 priority 120
Router1(config-if)#exit
Router1(config)#end
Router1#
Router2：
Router2#configure terminal
Enter configuration commands, one per line.;End with CNTL/Z.
Router2(config)#interface FastEthernet 1/0
Router2(config-if)#ip address 172.22.1.2 255.255.255.0
Router2(config-if)#standby 1 ip 172.22.1.1
Router2(config-if)#standby 1 priority 110 (默认priority is 100)
Router2(config-if)#exit
Router2(config)#end
Router2#
注释 由于HSRP虚拟出来的MAC地址跟组相关，所以可能会出现同一交换机收到多个相同的MAC地址的情况，这时候就需要用standby 1 mac-address 0000.0c07.ad01 命令来人工指定一个MAC地址
提问 强制某个路由器启动后一直在组中处于主用状态
回答
Router1#configure terminal
Enter configuration commands, one per line.;End with CNTL/Z.
Router1(config)#interface FastEthernet 0/1
Router1(config-if)#standby 1 ip 172.22.1.1
Router1(config-if)#standby 1 priority 120
Router1(config-if)#standby 1 preempt
Router1(config-if)#exit
Router1(config)#end
Router1#
Router2#configure terminal
Enter configuration commands, one per line.;End with CNTL/Z.
Router2(config)#interface FastEthernet 1/0
Router2(config-if)#standby 1 ip 172.22.1.1
Router2(config-if)#standby 1 priority 110
