在没有配置分发列表前各路由器的路由表：
R1:
r1#sh ip rou
C 192.168.12.0/24 is directly connected, Serial0/0
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.10.10.0 is directly connected, Loopback1
O 192.168.23.0/24 [110/128] via 192.168.12.2, 00:01:45, Serial0/0
r1#
R2：
r2#sh ip rou
C 192.168.12.0/24 is directly connected, Serial0/0
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/65] via 192.168.12.1, 00:01:32, Serial0/0
10.0.0.0/24 is subnetted, 1 subnets
O 10.10.10.0 [110/65] via 192.168.12.1, 00:01:32, Serial0/0
C 192.168.23.0/24 is directly connected, Serial0/1
r2#
R3:
r3#sh ip rou
O 192.168.12.0/24 [110/128] via 192.168.23.1, 00:01:14, Serial0/0
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/129] via 192.168.23.1, 00:01:14, Serial0/0
10.0.0.0/24 is subnetted, 1 subnets
O 10.10.10.0 [110/129] via 192.168.23.1, 00:01:14, Serial0/0
C 192.168.23.0/24 is directly connected, Serial0/0
r3#
可以看到各路由器都学习到了全网的路由。下面配置分发列表：
配置参数：
r2(config)#acc 1 den 10.10.10.0
r2(config)#acc 1 per an
r2(config)#router os 1
r2(config-router)#distrib 1 in s0/0
查看配置效果：
r2#sh ip rou
C 192.168.12.0/24 is directly connected, Serial0/0
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/65] via 192.168.12.1, 00:00:26, Serial0/0
C 192.168.23.0/24 is directly connected, Serial0/1
r2#
可以看到R2的路由表中没有10.10.10.0/24的路由了，但R3的路由表中还是有的，
R3:
r3#clear ip route *
r3#sh ip rou
O 192.168.12.0/24 [110/128] via 192.168.23.1, 00:00:01, Serial0/0
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/129] via 192.168.23.1, 00:00:01, Serial0/0
10.0.0.0/24 is subnetted, 1 subnets
O 10.10.10.0 [110/129] via 192.168.23.1, 00:00:01, Serial0/0
C 192.168.23.0/24 is directly connected, Serial0/0
r3#
因为OSPF是链路状态路由协议，是通过LSA来更新路由表的。下面可以在R2查看10.10.10.0/24的LSA.
OSPF Router with ID (192.168.23.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
10.10.10.10 10.10.10.10 339 0x80000004 0x00C3DC 4
192.168.23.1 192.168.23.1 346 0x80000004 0x00D194 4
192.168.23.2 192.168.23.2 382 0x80000002 0x000416 2
r2#
r2#show ip os database router 10.10.10.10
OSPF Router with ID (192.168.23.1) (Process ID 1)
Router Link States (Area 0)
LS age: 368
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 10.10.10.10
Advertising Router: 10.10.10.10
LS Seq Number: 80000004
Checksum: 0xC3DC
Length: 72
Number of Links: 4
Link connected to: a Stub Network
(Link ID) Network/subnet number: 10.10.10.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 1
Link connected to: a Stub Network
(Link ID) Network/subnet number: 1.1.1.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 1
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID: 192.168.23.1
(Link Data) Router Interface address: 192.168.12.1
Number of TOS metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 192.168.12.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 64
r2#
可以得出分发列表的IN方向在OSPF中只能到本路由器有作用！！！
本文转自810105851 51CTO博客，原文链接：http://blog.51cto.com/4708948/1131402，如需转载请自行联系原作者
