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本文主要描述通过策略路由PBR和IP服务水平协议SLA来实现数据包的分流。
假设：Outside上设置默认路由到192.168.1.0/24，下一条指向R6：ip route 0.0.0.0 255.255.255.0 1.1.56.6
要求：但是从源IP:5.5.5.5/32出来的数据包必须走R4：并且保证链路的畅通性：
R5基本配置：
interface Loopback0
ip address 5.5.5.5 255.255.255.255
interface FastEthernet1/0
ip address 1.1.56.5 255.255.255.0
interface FastEthernet1/1
ip address 1.1.45.5 255.255.255.0
ip policy route-map AAA
ip local policy route-map AAA
ip route 0.0.0.0 0.0.0.0 1.1.56.6
route-map AAA permit 10
match interface Loopback0
set ip next-hop 1.1.45.4
R5#debug ip policy
R5#ping 4.4.4.4 sou lo0 ：这里注意：如果是本地产生的流量，route-map默认是不匹配的，需要启用：[ip local policy route-map AAA]：才能让本地流量匹配AAA：
*Dec 3 18:48:32.823: IP: s=5.5.5.5 (local), d=4.4.4.4, len 100, policy match
*Dec 3 18:48:32.823: IP: route map AAA, item 10, permit
*Dec 3 18:48:32.827: IP: s=5.5.5.5 (local), d=4.4.4.4 (FastEthernet1/1), len 100, policy routed
*Dec 3 18:48:32.827: IP: local to FastEthernet1/1 1.1.45.4
此时如果关闭R4的F1/1接口：此时R5再pingR4：链路是否正常？
【不通】：解释：route-map无法区分下一跳是否可达。但是可以结合SLA来实现：
ip sla monitor 1
type echo protocol ipIcmpEcho 1.1.45.4
frequency 10
ip sla monitor schedule 1 life forever start-time now
track 2 rtr 1
route-map AAA permit 10
match interface Loopback0
set ip next-hop verify-availability 1.1.45.4 1 track 2
R5#ping 4.4.4.4 sou lo0 ：这里注意：此时如果你关闭R4的F1/1，即使流量匹配了route-map，但是策略还是不会被执行，走正常的路由表：详细见以下debug信息
Wan30#debug ip policy
*Dec 3 18:49:42.115: IP: s=5.5.5.5 (local), d=4.4.4.4, len 100, policy match
*Dec 3 18:49:42.115: IP: route map AAA, item 10, permit
*Dec 3 18:49:42.115: IP: s=5.5.5.5 (local), d=4.4.4.4, len 100, policy rejected -- normal forwarding
通过以上配置实验，数据包分流实现。
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