使用分发列表过滤路由及路由汇总、防环的实验

这个实验是采用分发列表来实现路由过滤和汇总、防环的功能，这次的拓扑图如下：

说明：IP及接口配置如上所示，左边运行OSPF，右边运行EIGRP

实验目的：掌握用分发列表来过滤路由

在重分布路由时使用路由汇总来降低路由器的负担，以及带来的问题

具体要求：R2过滤掉1.1.1.0的路由，R5在向R4通告的时候过滤掉172.16.55.0的路由。

Ospf向eigrp通告路由时将路由汇总10.0.0.0/8的

Eigrp向Ospf通告路由时将路由汇总成172.16.0.0/16的

环回口路由可以不用汇总

实验步骤：

1. 配置IP地址以及路由协议

2. 在R3上配置重分布

配置命令：

router eigrp 90

redistribute ospf 110 metric 1544 100 255 1 1500

network 33.33.33.0 0.0.0.255

network 172.16.34.0 0.0.0.255

no auto-summary

!

router ospf 110

router-id 3.3.3.3

log-adjacency-changes

redistribute eigrp 90 subnets tag 8888

network 3.3.3.0 0.0.0.255 area 0

network 10.2.2.0 0.0.0.255 area 0

R1#show ip route

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

2.0.0.0/24 is subnetted, 1 subnets

O 2.2.2.0 [110/65] via 10.1.1.2, 00:21:34, Serial0/0

33.0.0.0/24 is subnetted, 1 subnets

O E2 33.33.33.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/129] via 10.1.1.2, 00:21:34, Serial0/0

4.0.0.0/24 is subnetted, 1 subnets

O E2 4.4.4.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

172.16.0.0/24 is subnetted, 3 subnets

O E2 172.16.55.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

O E2 172.16.45.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

O E2 172.16.34.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

10.0.0.0/24 is subnetted, 2 subnets

O 10.2.2.0 [110/128] via 10.1.1.2, 00:21:37, Serial0/0

C 10.1.1.0 is directly connected, Serial0/0

此时，所有路由器都有所有的路由。

3. 在R2上配置分发列表过滤路由1.1.1.0

R2(config)#ip access-list stan 10

R2(config-std-nacl)#10 deny 1.1.1.0

R2(config-std-nacl)#20 permit any

R2(config)#router ospf 110

R2(config-router)#distribute-list 10 in s0/0

配置结果查看：

R2#show ip route

2.0.0.0/24 is subnetted, 1 subnets

C 2.2.2.0 is directly connected, Loopback0

33.0.0.0/24 is subnetted, 1 subnets

O E2 33.33.33.0 [110/20] via 10.2.2.3, 00:00:17, Serial0/1

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/65] via 10.2.2.3, 00:00:17, Serial0/1

4.0.0.0/24 is subnetted, 1 subnets

O E2 4.4.4.0 [110/20] via 10.2.2.3, 00:00:17, Serial0/1

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 10.2.2.3, 00:00:17, Serial0/1

172.16.0.0/24 is subnetted, 3 subnets

O E2 172.16.55.0 [110/20] via 10.2.2.3, 00:00:17, Serial0/1

O E2 172.16.45.0 [110/20] via 10.2.2.3, 00:00:17, Serial0/1

O E2 172.16.34.0 [110/20] via 10.2.2.3, 00:00:18, Serial0/1

10.0.0.0/24 is subnetted, 2 subnets

C 10.2.2.0 is directly connected, Serial0/1

C 10.1.1.0 is directly connected, Serial0/0

此时R2上面已经没有1.1.1.0的路由，但R3的路由表中还有此条路由

R3#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

O 1.1.1.0 [110/129] via 10.2.2.2, 00:29:56, Serial0/1

2.0.0.0/24 is subnetted, 1 subnets

O 2.2.2.0 [110/65] via 10.2.2.2, 00:29:56, Serial0/1

33.0.0.0/24 is subnetted, 1 subnets

C 33.33.33.0 is directly connected, Loopback1

3.0.0.0/24 is subnetted, 1 subnets

C 3.3.3.0 is directly connected, Loopback0

4.0.0.0/24 is subnetted, 1 subnets

D 4.4.4.0 [90/2297856] via 172.16.34.4, 00:31:50, Serial0/2

5.0.0.0/24 is subnetted, 1 subnets

D 5.5.5.0 [90/2809856] via 172.16.34.4, 00:31:19, Serial0/2

172.16.0.0/24 is subnetted, 3 subnets

D 172.16.55.0 [90/2809856] via 172.16.34.4, 00:31:27, Serial0/2

D 172.16.45.0 [90/2681856] via 172.16.34.4, 00:31:58, Serial0/2

C 172.16.34.0 is directly connected, Serial0/2

10.0.0.0/24 is subnetted, 2 subnets

C 10.2.2.0 is directly connected, Serial0/1

10.1.1.0 [110/128] via 10.2.2.2, 00:29:57, Serial0/1

4. 在R5上配置分发列表过滤路由

R5(config)#ip access-list stan 10

R5(config-std-nacl)#10 deny 172.16.55.0

R5(config-std-nacl)#20 permit any

R5(config-std-nacl)#exit

R5(config)#router eigrp 90

R5(config-router)#distribute-list 10 out s0/3

R5(config-router)#end

R5#

*Mar 1 04:39:42.830: %SYS-5-CONFIG_I: Configured from console by console

R5#

*Mar 1 04:39:51.734: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 90: Neighbor 172.16.45.4 (Serial0/3) is resync: route configuration changed

当邻居重新建立以后，再看R4的路由表

R4#show ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

D EX 1.1.1.0 [170/2195456] via 172.16.34.3, 00:34:14, Serial0/2

2.0.0.0/24 is subnetted, 1 subnets

D EX 2.2.2.0 [170/2195456] via 172.16.34.3, 00:34:14, Serial0/2

33.0.0.0/24 is subnetted, 1 subnets

D 33.33.33.0 [90/2297856] via 172.16.34.3, 00:36:52, Serial0/2

3.0.0.0/24 is subnetted, 1 subnets

D EX 3.3.3.0 [170/2195456] via 172.16.34.3, 00:34:14, Serial0/2

4.0.0.0/24 is subnetted, 1 subnets

C 4.4.4.0 is directly connected, Loopback0

5.0.0.0/24 is subnetted, 1 subnets

D 5.5.5.0 [90/2297856] via 172.16.45.5, 00:36:08, Serial0/3

172.16.0.0/24 is subnetted, 2 subnets

C 172.16.45.0 is directly connected, Serial0/3

C 172.16.34.0 is directly connected, Serial0/2

10.0.0.0/24 is subnetted, 2 subnets

D EX 10.2.2.0 [170/2195456] via 172.16.34.3, 00:34:14, Serial0/2

D EX 10.1.1.0 [170/2195456] via 172.16.34.3, 00:34:14, Serial0/2

结果：R4上已经没有了172.16.55.0的路由

5. 在R3上做路由汇总

R3(config)#int s0/2

R3(config-if)#ip summary-address eigrp 90 10.0.0.0 255.0.0.0

R3(config-if)#router ospf 110

R3(config-router)#summary-address 172.16.0.0 255.255.0.0

在R1和R5上分别看路由表

汇总前：

R1#show ip route

Gateway of last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

2.0.0.0/24 is subnetted, 1 subnets

O 2.2.2.0 [110/65] via 10.1.1.2, 00:21:34, Serial0/0

33.0.0.0/24 is subnetted, 1 subnets

O E2 33.33.33.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/129] via 10.1.1.2, 00:21:34, Serial0/0

4.0.0.0/24 is subnetted, 1 subnets
http://www.luyouqiwang.com/15220
O E2 4.4.4.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 10.1.1.2, 00:21:34, Serial0/0

172.16.0.0/24 is subnetted, 3 subnets

O E2 172.16.55.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

O E2 172.16.45.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

O E2 172.16.34.0 [110/20] via 10.1.1.2, 00:21:37, Serial0/0

10.0.0.0/24 is subnetted, 2 subnets

O 10.2.2.0 [110/128] via 10.1.1.2, 00:21:37, Serial0/0

C 10.1.1.0 is directly connected, Serial0/0

汇总路由以后

R1#show ip rou

R1#show ip route

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

2.0.0.0/24 is subnetted, 1 subnets

O 2.2.2.0 [110/65] via 10.1.1.2, 00:39:01, Serial0/0

33.0.0.0/24 is subnetted, 1 subnets

O E2 33.33.33.0 [110/20] via 10.1.1.2, 00:39:01, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/129] via 10.1.1.2, 00:39:01, Serial0/0

4.0.0.0/24 is subnetted, 1 subnets

O E2 4.4.4.0 [110/20] via 10.1.1.2, 00:39:01, Serial0/0

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 10.1.1.2, 00:39:01, Serial0/0

O E2 172.16.0.0/16 [110/20] via 10.1.1.2, 00:01:09, Serial0/0

10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks

O 10.2.2.0/24 [110/128] via 10.1.1.2, 00:39:01, Serial0/0

C 10.1.1.0/24 is directly connected, Serial0/0

O E2 10.0.0.0/8 [110/20] via 10.1.1.2, 00:01:37, Serial0/0

实验结果：

在R1上看汇总路由的结果，经过汇总，确实把Eigrp传过来的路由已经汇总成了172.16.0.0，但是，同样在R1上可以看到还有一条10.0.0.0/8的汇总路由，是从EIGRP重分布过来的，实际上这是一条不需要的路由或者可以说是产生了环路。

6. 在R3上做路由重分布的过滤，防止环路的发生

解决环路，双进行重分布的路由器上面做分发列表，拒绝某路由协议域的汇总路由通过重分布再回到该路由域

R3上的配置

router eigrp 90

redistribute ospf 110 metric 1544 100 255 1 1500

network 33.33.33.0 0.0.0.255

network 172.16.34.0 0.0.0.255

distribute-list 30 out ospf 110

no auto-summary

access-list 30 deny 172.16.0.0

access-list 30 permit any

!

router ospf 110

router-id 3.3.3.3

summary-address 172.16.0.0 255.255.0.0

redistribute eigrp 90 subnets tag 8888

network 3.3.3.0 0.0.0.255 area 0

network 10.2.2.0 0.0.0.255 area 0

distribute-list 20 out eigrp 90

!

access-list 20 deny 10.0.0.0

access-list 20 permit any

此时再查看R1的路由表，已经没有了该条10.0.0.0/8的路由

R1#show ip route

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

2.0.0.0/24 is subnetted, 1 subnets

O 2.2.2.0 [110/65] via 10.1.1.2, 01:00:35, Serial0/0

33.0.0.0/24 is subnetted, 1 subnets

O E2 33.33.33.0 [110/20] via 10.1.1.2, 01:00:35, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/129] via 10.1.1.2, 01:00:35, Serial0/0

4.0.0.0/24 is subnetted, 1 subnets

O E2 4.4.4.0 [110/20] via 10.1.1.2, 01:00:35, Serial0/0

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 10.1.1.2, 01:00:35, Serial0/0

O E2 172.16.0.0/16 [110/20] via 10.1.1.2, 00:22:43, Serial0/0

10.0.0.0/24 is subnetted, 2 subnets

O 10.2.2.0 [110/128] via 10.1.1.2, 01:00:35, Serial0/0

C 10.1.1.0 is directly connected, Serial0/0

注意：在运行OSPF路由协议的路由器之间使用分发列表时，不允许使用接口上的out，允许使用接口in，但是使用接口in只影响本台路由器，对下游OSPF路由器是不会产生影响的，因为通告是LSA而不是路由。