Prefix-List

Prefix-List

和ACL类似的东东，设计用于专抓路由的工具，不仅可以匹配网络号，还可以匹配掩码

R4(config)#ip prefix-list 2（用名字也行） permit 2.2.2.0/24
R4(config-router)#distribute-list prefix 2 in serial 1

例一：
ip prefix-list 2 permit 2.2.2.0/24　　　　　　　//（匹配前24位:2.2.2.* ，掩码必须为24位）

例二：
ip prefix-list 2 permit 2.2.2.0/24 ge 25 le 30　//（匹配前24位:2.2.2.* ，掩码必须为25-30位）

例三：
ip prefix-list 2 permit 2.2.2.0/24 le 32　　　　//（匹配前24位:2.2.2.* ，掩码必须为24-32位）

例四：
ip prefix-list 2 permit 2.2.2.0/24 ge 26　　　　//（匹配前24位:2.2.2.* ，掩码必须为26-32位）

例五：
ip prefix-list 3 permit 0.0.0.0/0 le 32　　　　 //（匹配所有）不能像access-list哪样用any参数

ge必须大于前面的数字，小或等于le ,len<ge-value<=le-value

sh ip prefix-list用于查看

用前缀列表过滤A、B、C类路由
A类路由：ip prefix-list 1 permit 0.0.0.0/1 le 32
B类路由：ip prefix-list 1 permit 128.0.0.0/2 le 32
C类路由：ip prefix-list 1 permit 192.0.0.0/3 le 32
 

案例1:拓扑如下所示:

R1(s1/1)------(s1/0)R2(s1/1)------(s1/0)R3

在R2上有六个环回接口，现在要使R3只能收到掩码为17,18,19的三条网络。六个环回口分别为172.16.128.1/17,172.16.64.1/18,172.16.32.1/19,172.16.16.1/20,172.16.8.1/21,172.16.4.1/22

当配置完成后，先看一看R3的路由表:

R3#sh ip ro ei
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/2297856] via 13.1.1.1, 00:00:06, Serial1/0
2.0.0.0/24 is subnetted, 1 subnets
D 2.2.2.0 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
172.16.0.0/16 is variably subnetted, 6 subnets, 6 masks
D 172.16.128.0/17 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
D 172.16.32.0/19 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
D 172.16.16.0/20 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
D 172.16.8.0/21 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
D 172.16.4.0/22 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
D 172.16.64.0/18 [90/2809856] via 13.1.1.1, 00:00:06, Serial1/0
12.0.0.0/24 is subnetted, 1 subnets
D 12.1.1.0 [90/2681856] via 13.1.1.1, 00:00:06, Serial1/0

现在，在R1上做配置来满足需求:

R1#sh run | b r e
distribute-list prefix 1 out Serial1/1
!
ip prefix-list 1 seq 5 permit 172.16.0.0/16 ge 17 le 19

此时，我们再来看一看R3的路由表:

R3#sh ip ro ei
172.16.0.0/16 is variably subnetted, 3 subnets, 3 masks
D 172.16.128.0/17 [90/2809856] via 13.1.1.1, 00:01:01, Serial1/0
D 172.16.32.0/19 [90/2809856] via 13.1.1.1, 00:01:01, Serial1/0
D 172.16.64.0/18 [90/2809856] via 13.1.1.1, 00:01:01, Serial1/0

R2的配置:

R2#sh run | b r e
router eigrp 100
network 2.2.2.2 0.0.0.0
network 12.1.1.0 0.0.0.255
network 172.16.0.0
no auto-summary
R1的配置:

R3#sh run | b r e
router eigrp 100
network 3.3.3.3 0.0.0.0
network 13.1.1.0 0.0.0.255
no auto-summary

R3的配置:

R1# sh run | b r e
router eigrp 100
network 1.1.1.1 0.0.0.0
network 12.1.1.0 0.0.0.255
network 13.1.1.0 0.0.0.255
distribute-list prefix 1 out Serial1/1
no auto-summary
!
ip prefix-list 1 seq 5 permit 172.16.0.0/16 ge 17 le 19

案例2:利用前缀列表过滤OSPF

要求：在如上图所示的拓朴中，在R1上利用前缀列表做过滤，不要向AREA0区域传递172.16.1.1的路由。

看一看R3的路由表:

R3#sh ip ro os
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/65] via 13.1.1.1, 00:00:55, Serial0/1
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/129] via 13.1.1.1, 00:00:55, Serial0/1
172.16.0.0/32 is subnetted, 2 subnets
O IA 172.16.1.1 [110/129] via 13.1.1.1, 00:00:55, Serial0/1
O IA 172.16.2.1 [110/129] via 13.1.1.1, 00:00:55, Serial0/1
12.0.0.0/24 is subnetted, 1 subnets
O IA 12.1.1.0 [110/128] via 13.1.1.1, 00:00:55, Serial0/1

在R1上配置，满足需求:

R1#sh run | b r o
area 1 filter-list prefix 1 out
!
ip prefix-list 1 seq 5 deny 172.16.1.1/32
ip prefix-list 1 seq 10 permit 0.0.0.0/0 le 32

此时，再看一看R3的路由表:

R3#sh ip ro os
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/65] via 13.1.1.1, 00:03:07, Serial0/1
2.0.0.0/32 is subnetted, 1 subnets
O IA 2.2.2.2 [110/129] via 13.1.1.1, 00:03:07, Serial0/1
172.16.0.0/32 is subnetted, 1 subnets
O IA 172.16.2.1 [110/129] via 13.1.1.1, 00:03:07, Serial0/1
12.0.0.0/24 is subnetted, 1 subnets
O IA 12.1.1.0 [110/128] via 13.1.1.1, 00:03:07, Serial0/1

各路由器的配置:

R2的配置:

R2#sh run | b r o
router ospf 110
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.2 0.0.0.0 area 1
network 12.1.1.2 0.0.0.0 area 1
network 172.16.0.0 0.0.255.255 area 1

R1的配置:

R1#sh run | b r o
router ospf 110
router-id 1.1.1.1
log-adjacency-changes
area 1 filter-list prefix 1 out
network 1.1.1.1 0.0.0.0 area 0
network 12.1.1.1 0.0.0.0 area 1
network 13.1.1.1 0.0.0.0 area 0
!
ip prefix-list 1 seq 5 deny 172.16.1.1/32
ip prefix-list 1 seq 10 permit 0.0.0.0/0 le 32

R3的配置:

R3#sh run | b r o
router ospf 110
router-id 3.3.3.3
log-adjacency-changes
network 3.3.3.3 0.0.0.0 area 0
network 13.1.1.3 0.0.0.0 area 0