路由能够基于网络号过滤到或来自于某个特定邻居的路由更新。由访问列表组成的过滤器被应用到所有发送到或来自于某个特定邻居的BGP更新上。

 

本案例中，我们在R1上配置一个distribute-list，防止1.0.0.0/8被通告入AS200中。

 

 

//// r1 ////

int f2/0

  ip ad 192.1.1.1 255.255.255.0

 

int f3/0

  ip ad 193.1.1.1 255.255.255.0

 

int lo0

  ip ad 1.1.1.1 255.255.255.0

 

int lo1

  ip ad 2.2.2.2 255.255.255.0

 

router bgp 100

  no syn

  neighbor 192.1.1.2 remote-as 200

  neighbor 193.1.1.3 remote-as 200

  network 1.0.0.0

  network 1.0.0.0

 

 

//// r2 ////

int f2/0

  ip ad 192.1.1.2 255.255.255.0

 

int f4/0

  ip ad 194.1.1.2 255.255.255.0

 

router os 1

  netw 0.0.0.0 255.255.255.255 a 0

  passive-interface f2/0

 

router bgp 200

  no syn

  neighbor 192.1.1.1 remote-as 100

  neighbor 194.1.1.4 remote-as 200

  neighbor 195.1.1.3 remote-as 200

  neighbor 194.1.1.4 next-hop-self

 

 

//// r3 ////

int f3/0

  ip ad 193.1.1.3 255.255.255.0

 

int f5/0

  ip ad 195.1.1.3 255.255.255.0

 

router os 1

  netw 0.0.0.0 255.255.255.255 a 0

  passive-interface f3/0

 

router bgp 200

  no syn

  neighbor 193.1.1.1 remote-as 100

  neighbor 195.1.1.4 remote-as 200

  neighbor 195.1.1.4 next-hop-self

  neighbor 194.1.1.2 remote-as 200

//// r4 ////

int f4/0

  ip ad 194.1.1.4 255.255.255.0

 

int f5/0

  ip ad 195.1.1.4 255.255.255.0

 

int lo0

  ip ad 4.4.4.4 255.255.255.0

 

router os 1

  netw 0.0.0.0 255.255.255.255 a 0

 

router bgp 200

  no syn

  neighbor 194.1.1.2 remote-as 200

  neighbor 195.1.1.3 remote-as 200

  netw 4.0.0.0

 

 

 

验证：

r2#sh ip bgp
   Network          Next Hop            Metric LocPrf Weight Path
*> 1.0.0.0          192.1.1.1                0             0 100 i
* i2.0.0.0          193.1.1.1                0    100      0 100 i
*>                  192.1.1.1                0             0 100 i
*>i4.0.0.0          194.1.1.4                0    100      0 i

 

由193.1.1.1学来的1.0.0.0/8路由条目已被过滤！