19、BGP配置之Preferred Value 选路二

一、实验拓扑

二、实验需求

1、配置全网互通。BGP中引入IGP路由条目3.3.3.0

2、在AS 100 内采用RIPv2 协议配置IGP

3、在R1 R2 R4 上配置静态路由，保证R1 R2的Loopback 0 接口和R4 的Loopback 0 能建立 TCP会话

4、配置BGP协议，用环回口建立邻居，R3 将33.33.33.0、3.3.3.0 R4将 44.44.44.0 、55.55.55.0通告进BGP进程中

5、配置R3访问55.55.55.55从R2过

• BG路由属性的比较过程中，首先要比较的就是路由信息首选值 Preference Value,也简称为 PreVal. 值越大，优先级越高，默认为 0，Preference Value,不会发送给任何BGP邻居，仅作为本地路由器用来选路使用。

  三、实验过程

  1、R1的配置

  undo ter mo
  sys
  sysname R1
  user-interface console 0
  idle-timeout 0 0
  int loop 0
  ip add 1.1.1.1 24
  int g0/0/0
  ip add 192.168.13.1 24
  int g0/0/1
  ip add 192.168.14.1 24
  rip
  version 2
  network 192.168.13.0
  network 1.0.0.0
  ip route-static 4.4.4.0 255.255.255.0 192.168.14.4
  bgp 100
  router-id 1.1.1.1
  peer 2.2.2.2 as-number 100
  peer 2.2.2.2 connect-interface loopback 0
  peer 2.2.2.2 next-hop-local
  peer 3.3.3.3 as-number 100
  peer 3.3.3.3 connect-interface loopback 0
  peer 3.3.3.3 next-hop-local
  peer 4.4.4.4 as-number 200
  peer 4.4.4.4 connect-interface loopback 0
  peer 4.4.4.4 ebgp-max-hop 
  network  3.3.3.0 255.255.255.0
  

  2、R2的配置

  undo ter mo
  sys
  sysname R2
  user-interface console 0
  idle-timeout 0 0
  int loop 0
  ip add 2.2.2.2 24
  int g0/0/1
  ip add 192.168.23.2 24
  int g0/0/0
  ip add 192.168.24.2 24
  rip
  version 2
  network 192.168.23.0
  network 2.0.0.0
  ip route-static 4.4.4.0 255.255.255.0 192.168.24.4
  bgp 100
  router-id 2.2.2.2
  peer 1.1.1.1 as-number 100
  peer 1.1.1.1 connect-interface loopback 0
  peer 1.1.1.1 next-hop-local
  peer 3.3.3.3 as-number 100
  peer 3.3.3.3 connect-interface loopback 0
  peer 3.3.3.3 next-hop-local
  peer 4.4.4.4 as-number 200
  peer 4.4.4.4 connect-interface loopback 0
  peer 4.4.4.4 ebgp-max-hop 
  network  3.3.3.0 255.255.255.0
  

  3、R3的配置

  undo ter mo
  sys
  sysname R3
  user-interface console 0
  idle-timeout 0 0
  int loop 0
  ip add 3.3.3.3 24
  int loop 1
  ip add 33.33.33.33 24
  int g0/0/0
  ip add 192.168.13.3 24
  int g0/0/1
  ip add 192.168.23.3 24
  rip
  version 2
  network 192.168.13.0
  network 192.168.23.0
  network 3.0.0.0
  ip ip-prefix 1  permit 55.55.55.0 24
  route-policy 10 permit node 1
  if-match ip-prefix 1
  apply preferred-value 99
  route-policy 10 permit node 2
  bgp 100
  router-id 3.3.3.3
  peer 1.1.1.1 as-number 100
  peer 1.1.1.1 connect-interface loopback 0
  peer 2.2.2.2 as-number 100
  peer 2.2.2.2 connect-interface loopback 0
  peer 2.2.2.2 route-policy 10 import
  network 33.33.33.0 24
  

  4、R4的配置

  undo ter mo
  sys
  sysname R4
  user-interface console 0
  idle-timeout 0 0
  int loop 0
  ip add 4.4.4.4 24
  int loop 1
  ip add 44.44.44.44 24
  int loop 2
  ip add 55.55.55.55 24
  int g0/0/0
  ip add 192.168.14.4 24
  int g0/0/1
  ip add 192.168.24.4 24
  ip route-static 1.1.1.0 255.255.255.0 192.168.14.1
  ip route-static 2.2.2.0 255.255.255.0 192.168.24.2
  bgp 200
  router-id 4.4.4.4
  peer 1.1.1.1 as-number 100
  peer 1.1.1.1 connect-interface loopback 0
  peer 1.1.1.1 ebgp-max-hop 
  peer 2.2.2.2 as-number 100
  peer 2.2.2.2 connect-interface loopback 0
  peer 2.2.2.2 ebgp-max-hop 
  network 44.44.44.0 24
  network 55.55.55.0 24
  

  四、实验结果

  1、查看R3的BGP路由表

  

  2、查看R1的BGP路由信息

  
• 在R3 上修改之后，R1 R2 上的PrefVal 值不变，说明了PrefVal 值只作为本地路由器用来选路使用，并不传递给任何BGP 邻居。

  3、测试源地址3.3.3.3与44.44.44.44的连通性