OSPF_7类LSA转发地址分析.doc

OSPF 7类LSA转发地址分析：以上图为例进行分析：分析的前提均将lo0设为了router-id，没做额外的修改。（1）、首先分析RT2的lo0没有通告进Area 2，E3/0、E3/1、E3/2、E3/3口通告进了Area 2，RT6的E3/0、E3/1、E3/2、E3/3口通告进了Area 2，lo0通告进Area 0RT6#show ip ospf database nssa-external OSPF Router with ID (6.6.6.6) (Process ID 1) Type-7 AS External Link States (Area 2) LS age: 23 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 0.0.0.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x6221 Length: 36 Network Mask: /0 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 1 Forward Address: 10.2.9.1 External Route Tag: 0 LS age: 22 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 4.4.4.4 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xAA74 Length: 36 Network Mask: /32 Metric Type: 1 (Comparable directly to link state metric) TOS: 0 Metric: 1000 Forward Address: 10.2.5.1 External Route Tag: 0 LS age: 23 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 172.16.4.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xB1BC Length: 36 Network Mask: /24 Metric Type: 1 (Comparable directly to link state metric) TOS: 0 Metric: 1000 Forward Address: 10.2.5.1 External Route Tag: 0RT6#在这种情况下，转发地址选择的是通告进Area 2来的业务网段中最大的一个地址作为转发地址。（2）将业务网段全部改为重发布，而非直接参与OSPF进程，以外部路由的形式进入OSPF进程。RT6#show ip ospf database nssa-external OSPF Router with ID (6.6.6.6) (Process ID 1) Type-7 AS External Link States (Area 2) LS age: 34 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 0.0.0.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x4E23 Length: 36 Network Mask: /0 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 1 Forward Address: 10.2.26.2 External Route Tag: 0LS age: 37 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 10.2.9.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0xF3A Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 10.2.26.2 External Route Tag: 0 Routing Bit Set on this LSA LS age: 33 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 2.2.2.2 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xA2BC Length: 36 Network Mask: /32 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 10.2.26.1 External Route Tag: 0 Routing Bit Set on this LSA LS age: 34 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 4.4.4.4 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0x2ED1 Length: 36 Network Mask: /32 Metric Type: 1 (Comparable directly to link state metric) TOS: 0 Metric: 1000 Forward Address: 10.2.26.1 External Route Tag: 0RT6#此时有了明显的变化，凡是经过RT2通告进来的路由，转发地址变成了RT2上唯一参与了ospf进程的接口了。RT6上也全是唯一参与Area 2的接口为转发地址（3）、将RT2上的lo0通告进ospf 进程，业务网段仍然以重发布的形式发布进ospf进程。RT2为Area 2,RT6 为Area 0RT6#show ip ospf database nssa-external OSPF Router with ID (6.6.6.6) (Process ID 1) Type-7 AS External Link States (Area 2) LS age: 25 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 0.0.0.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x4E23 Length: 36 Network Mask: /0 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 1 Forward Address: 10.2.26.2 External Route Tag: 0 Routing Bit Set on this LSA LS age: 26 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 4.4.4.4 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xAA74 Length: 36 Network Mask: /32 Metric Type: 1 (Comparable directly to link state metric) TOS: 0 Metric: 1000 Forward Address: 2.2.2.2 External Route Tag: 0 Routing Bit Set on this LSA LS age: 29 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 10.2.2.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xCAAD Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 2.2.2.2 External Route Tag: 0 LS age: 31 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 10.2.6.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x301C Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 10.2.26.2 External Route Tag: 0RT6#由RT2通告的路由转发地址全部改为了RT2 的lo0接口。RT6的仍为唯一参与Area 2的接口地址。接下来将RT6的lo0改为Area 2：RT6#show ip ospf database nssa-external OSPF Router with ID (6.6.6.6) (Process ID 1) Type-7 AS External Link States (Area 2) LS age: 17 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 0.0.0.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x85FB Length: 36 Network Mask: /0 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 1 Forward Address: 6.6.6.6 External Route Tag: 0 Routing Bit Set on this LSA LS age: 17 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 4.4.4.4 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xAA74 Length: 36 Network Mask: /32 Metric Type: 1 (Comparable directly to link state metric) TOS: 0 Metric: 1000 Forward Address: 2.2.2.2 External Route Tag: 0 Routing Bit Set on this LSA LS age: 18 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 10.2.2.0 (External Network Number ) Advertising Router: 2.2.2.2 LS Seq Number: 80000001 Checksum: 0xCAAD Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 2.2.2.2 External Route Tag: 0 LS age: 18 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 10.2.6.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x67F4 Length: 36 Network Mask: /24 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 20 Forward Address: 6.6.6.6 External Route Tag: 0RT6#由RT6始发的路由的转发地址全部改为了RT6的lo0接口地址。（5）、将RT2、RT6上业务网段改为通告进入ospf进程。RT6#show ip ospf database nssa-external OSPF Router with ID (6.6.6.6) (Process ID 1) Type-7 AS External Link States (Area 2) LS age: 21 Options: (No TOS-capability, No Type 7/5 translation, DC) LS Type: AS External Link Link State ID: 0.0.0.0 (External Network Number ) Advertising Router: 6.6.6.6 LS Seq Number: 80000001 Checksum: 0x85FB Length: 36 Network Mask: /0 Metric Type: 2 (Larger than any link state path) TOS: 0 Metric: 1 Forward Address: 6.6.6.6 External Route Tag: 0 Routing Bit Set on this LSA LS age: 21 Options: (No TOS-capability, Type 7/5 translation, DC) LS Type: AS External Link Link State I