OSPF:LSA Type-7 to Type-5 转发地址抑制(实验)

 

1.LSA Type 7 to Type 5

1.1实验拓扑

1.2实验需求

1)按拓扑完成基本配置

2)重分发RIP网络进入OSPF进程,R2连接RIP域的接口网络同时也参与OSPF进程

3)观察R2上产生的LSA Type 7的转发地址

4)观察R3上作为ABRLSA Type 7转化为LSA Type 5后的转发地址

5)修改R2R3直连接口网络类型为点到点,观察实验现象

1.3实验步骤

1LSA Type 7转发地址

R2#show ip ospf database nssa-external | include Forward

        Forward Address: 31.31.12.1

此时转发地址继承原路由下一跳

 

2Type 7 to Type 5

R3#show ip ospf database external

 

            OSPF Router with ID (3.3.3.3) (Process ID 1)

 

                Type-5 AS External Link States

 

  LS age: 171

  Options: (No TOS-capability, DC)

  LS Type: AS External Link

  Link State ID: 1.1.1.0 (External Network Number )

  Advertising Router: 3.3.3.3

  LS Seq Number: 80000001

  Checksum: 0xDF66

  Length: 36

  Network Mask: /24

        Metric Type: 2 (Larger than any link state path)

        TOS: 0

        Metric: 20

        Forward Address: 31.31.12.1

        External Route Tag: 0

可见,当LSA Type 7转化为Type 5以后,通告者将变为NSSAABR,同时还会继承LSA Type 7中所携带的Forward Address

 

3修改接口网络类型

R2(config-if)#ip ospf network point-to-point

 

R3(config-if)#ip ospf network point-to-point

 

R3#show ip ospf database external | include Forward

        Forward Address: 31.31.12.1

对转发地址的继承并没有因为连接ASBR直连接口的网络类型改变而发生变化

1.4实验结论

LSA Type 7转化为LSA Type 5时,LSA Type 5会继承LSA Type 7中的转发地址

 

 

2.转发地址抑制

2.1实验拓扑

2.2实验需求

1)按拓扑完成基本配置

2)观察R4上接收到LSA Type 5的相关信息

3)在R4上写一条去往31.31.12.0网段,指向出口null0的静态路由,观察实验现象

4)在NSSA ABR R3上配置转发地址抑制,观察R4LSA Type 5的转发地址,同时验证去往R1环回口网络的可达性

2.3实验步骤

(1)查看LSA Type 5

R4#show ip ospf database external | in Forward

        Forward Address: 31.31.12.1

此时继承的下一跳伴随LSA Type 5扩散到OPSF域中

 

(2)静态路由

R4(config)#ip route 31.31.12.0 255.255.255.0 null 0

 

R4#show ip route ospf

     31.0.0.0/24 is subnetted, 3 subnets

O IA    31.31.23.0 [110/2] via 31.31.34.3, 00:15:25, FastEthernet0/0

此时外部网络消失,LSA Type 5被判定失效

 

3转发地址抑制

R3(config-router)#area 1 nssa translate type7 suppress-fa          //抑制转发地址继承

 

R4#show ip ospf database external | in Forward

        Forward Address: 0.0.0.0

此时LSA Type 7转化为LSA Type 5时,不再继承转发地址

 

R4#show ip route ospf

     1.0.0.0/24 is subnetted, 1 subnets

O E2    1.1.1.0 [110/20] via 31.31.34.3, 00:00:52, FastEthernet0/0

     31.0.0.0/24 is subnetted, 3 subnets

O IA    31.31.23.0 [110/2] via 31.31.34.3, 00:17:56, FastEthernet0/0

目标网络重新出现在路由表中

2.4实验结论

配置转发地址抑制后,新产生的LSA Type 5的转发地址将变为0.0.0.0

你可能感兴趣的:(ospf,转发地址抑制)